[Fix](expr) fix wrong debug string of cast expr and remove useless variable

[zclllyybb]

Proposed changes

Issue Number: close #xxx

before we print target type as the argument type.

and for target type, we only need type itself. don't need dummy column.

[doris-robot]

Thank you for your contribution to Apache Doris.
Don't know what should be done next? See How to process your PR

Since 2024-03-18, the Document has been moved to doris-website.
See Doris Document.

[zclllyybb]

run buildall

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[doris-robot]

TPC-H: Total hot run time: 41707 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpch-tools
Tpch sf100 test result on commit 7720753c123c073ab8794850adabfa2ec3a771cd, data reload: false

------ Round 1 ----------------------------------
q1	17588	7600	7283	7283
q2	2048	178	164	164
q3	10546	1152	1214	1152
q4	10232	814	842	814
q5	7743	3131	3060	3060
q6	238	153	150	150
q7	1025	602	599	599
q8	9627	2014	2031	2014
q9	7774	6427	6497	6427
q10	7149	2448	2433	2433
q11	462	247	247	247
q12	506	217	223	217
q13	17780	3010	3046	3010
q14	251	212	214	212
q15	564	519	514	514
q16	647	592	586	586
q17	988	521	629	521
q18	7321	6798	6793	6793
q19	1332	1057	1057	1057
q20	470	178	184	178
q21	4043	3288	3448	3288
q22	1086	988	1016	988
Total cold run time: 109420 ms
Total hot run time: 41707 ms

----- Round 2, with runtime_filter_mode=off -----
q1	7325	7861	7294	7294
q2	344	242	247	242
q3	3033	2842	2891	2842
q4	2043	1783	1774	1774
q5	5543	5586	5559	5559
q6	221	141	143	141
q7	2104	1725	1703	1703
q8	3261	3395	3432	3395
q9	8605	8567	8589	8567
q10	3481	3505	3453	3453
q11	579	491	510	491
q12	781	571	580	571
q13	7046	3020	3018	3018
q14	295	271	267	267
q15	559	508	508	508
q16	674	617	649	617
q17	1837	1579	1586	1579
q18	7765	7419	7559	7419
q19	1672	1607	1597	1597
q20	2070	1837	1801	1801
q21	5545	5287	5326	5287
q22	1111	1037	986	986
Total cold run time: 65894 ms
Total hot run time: 59111 ms

[doris-robot]

TeamCity be ut coverage result:
Function Coverage: 37.45% (9712/25932)
Line Coverage: 28.72% (80562/280546)
Region Coverage: 28.13% (41641/148018)
Branch Coverage: 24.69% (21157/85688)
Coverage Report: http://coverage.selectdb-in.cc/coverage/7720753c123c073ab8794850adabfa2ec3a771cd_7720753c123c073ab8794850adabfa2ec3a771cd/report/index.html

[doris-robot]

TPC-DS: Total hot run time: 192462 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpcds-tools
TPC-DS sf100 test result on commit 7720753c123c073ab8794850adabfa2ec3a771cd, data reload: false

query1	974	397	389	389
query2	6472	2040	2004	2004
query3	6116	211	231	211
query4	33638	23535	24091	23535
query5	3834	467	471	467
query6	255	180	176	176
query7	3415	296	294	294
query8	304	245	243	243
query9	6044	2670	2662	2662
query10	415	255	258	255
query11	18042	15405	15324	15324
query12	160	105	100	100
query13	1159	424	414	414
query14	8927	7588	7441	7441
query15	216	171	176	171
query16	7113	453	481	453
query17	912	539	524	524
query18	1816	286	293	286
query19	310	143	148	143
query20	114	105	104	104
query21	204	101	98	98
query22	4581	4272	4416	4272
query23	34811	34064	34208	34064
query24	11093	2789	2770	2770
query25	623	366	393	366
query26	1409	155	155	155
query27	2667	281	275	275
query28	7731	2391	2390	2390
query29	907	394	408	394
query30	288	169	161	161
query31	1024	795	838	795
query32	93	57	56	56
query33	755	267	253	253
query34	1025	508	504	504
query35	1043	886	882	882
query36	1118	939	946	939
query37	169	76	74	74
query38	4413	4316	4247	4247
query39	1471	1432	1409	1409
query40	261	98	96	96
query41	47	43	43	43
query42	107	105	96	96
query43	532	497	488	488
query44	1310	809	803	803
query45	178	165	170	165
query46	1128	697	692	692
query47	1946	1825	1830	1825
query48	411	323	321	321
query49	1024	381	379	379
query50	823	379	398	379
query51	7163	6927	6937	6927
query52	98	89	88	88
query53	254	174	187	174
query54	936	383	401	383
query55	80	73	77	73
query56	254	251	250	250
query57	1328	1145	1168	1145
query58	215	200	204	200
query59	3198	2990	2945	2945
query60	264	247	242	242
query61	106	103	100	100
query62	869	666	677	666
query63	213	189	181	181
query64	4497	629	656	629
query65	3300	3280	3225	3225
query66	1055	325	320	320
query67	16109	15816	15806	15806
query68	3233	582	598	582
query69	397	268	263	263
query70	1228	1192	1154	1154
query71	321	276	261	261
query72	6140	4136	4130	4130
query73	767	365	367	365
query74	9750	9057	9040	9040
query75	3433	2668	2685	2668
query76	1885	936	1010	936
query77	414	281	273	273
query78	10492	9644	9698	9644
query79	1291	587	605	587
query80	755	449	443	443
query81	535	244	253	244
query82	650	122	118	118
query83	215	153	140	140
query84	273	82	78	78
query85	1173	303	287	287
query86	344	320	305	305
query87	4990	4647	4631	4631
query88	3411	2207	2167	2167
query89	402	287	286	286
query90	1915	188	187	187
query91	130	100	101	100
query92	62	49	51	49
query93	1088	543	529	529
query94	739	284	292	284
query95	345	238	241	238
query96	613	279	275	275
query97	2848	2742	2779	2742
query98	205	202	200	200
query99	1556	1334	1315	1315
Total cold run time: 284967 ms
Total hot run time: 192462 ms

[doris-robot]

ClickBench: Total hot run time: 32.91 s

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/clickbench-tools
ClickBench test result on commit 7720753c123c073ab8794850adabfa2ec3a771cd, data reload: false

query1	0.03	0.03	0.03
query2	0.07	0.03	0.03
query3	0.23	0.06	0.06
query4	1.63	0.10	0.11
query5	0.41	0.40	0.37
query6	1.16	0.65	0.65
query7	0.02	0.02	0.02
query8	0.04	0.03	0.04
query9	0.57	0.50	0.50
query10	0.54	0.55	0.55
query11	0.17	0.12	0.10
query12	0.13	0.11	0.11
query13	0.60	0.60	0.60
query14	2.74	2.81	2.75
query15	0.91	0.85	0.83
query16	0.39	0.38	0.39
query17	1.09	0.99	1.02
query18	0.20	0.19	0.20
query19	1.93	1.82	1.94
query20	0.02	0.01	0.02
query21	15.36	0.62	0.60
query22	2.21	2.48	2.04
query23	17.09	1.01	0.86
query24	2.90	1.08	1.35
query25	0.27	0.06	0.14
query26	0.51	0.14	0.14
query27	0.05	0.05	0.04
query28	10.35	1.11	1.07
query29	12.58	3.36	3.32
query30	0.24	0.06	0.06
query31	2.86	0.37	0.38
query32	3.28	0.46	0.46
query33	2.98	3.06	3.05
query34	16.72	4.44	4.50
query35	4.50	4.41	4.49
query36	0.66	0.49	0.50
query37	0.09	0.06	0.06
query38	0.05	0.03	0.03
query39	0.03	0.03	0.02
query40	0.17	0.12	0.12
query41	0.07	0.03	0.02
query42	0.03	0.03	0.02
query43	0.03	0.03	0.03
Total cold run time: 105.91 s
Total hot run time: 32.91 s

[github-actions]

PR approved by at least one committer and no changes requested.

[github-actions]

PR approved by anyone and no changes requested.