Useful cli-options for mdbx_defrag

[erthink]

A set of new cli-options was added to the mdbx_defrag utility with refining defrag API and internals:

$ ./mdbx_defrag
usage: ./mdbx_defrag [-V] [-q] [-c] [-d] [-p] [-u|U] db_pathname
  -V		print version and exit
  -v		more verbose, could be repeated for extra details from debug-enabled builds.
  -q		be quiet.
  -1		perform a single quick defragmentation cycle without two-stage moves.
  -2 .. -9	limits the number of defragmentation cycles.
  -t seconds	limits the duration of defragmentation in seconds.
  -f percent	defragment until free up a given percentage of unused space (default 100).
  -r percent	acceptable undefragmented residue in percent of used space (0 by default).
  -s megabytes	preferred defragmentation step/transaction size.
  -c		force cooperative mode (don't try exclusive).
  -u		warmup database before defragmenting.
  -U		warmup and try lock database pages in memory before defragmenting.
  db_pathname	path to the database.

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Examples of running:

$ ./mdbx_defrag -7 -s 1024 test-28MiB.dat
mdbx_defrag v0.14.1-477-g051b7437 (2026-03-20T06:30:27+03:00, T-27b0aaea4bda4436bf8f7fad00661cca07368130)
Running for test-28MiB.dat...
 - space usage in pages: 1842682 allocated, payload 1331857, unused/GC 510825, pagesize 16384
 - defragmentation: target 100% (shrink 0 pages), cycles limit 7, step 65536 pages (1024 MiB), duration unlimited
 - loading the b-tree structure: 99.9%................................................................ done
 - cycle 1: 100.0%, moved 20012, left 510825.............................................................. large chunk
 - cycle 2: 100.0%, moved 65536, shrinked 7962, left 502863....... step size
 - cycle 3: 100.0%, moved 65536, shrinked 94620, left 416205............... step size
 - cycle 4: 100.0%, moved 65536, shrinked 182207, left 328618..................... step size
 - cycle 5: 100.0%, moved 65536, shrinked 268049, left 242776................. step size
 - cycle 6: 100.0%, moved 65536, shrinked 357846, left 152979................ step size
 - cycle 7: 100.0%, moved 47494, shrinked 443063, left 67762....... done
 - cycle 8: 0.0%, shrinked 443063, left 67762... discontinued by user
Defragmentation: shrinked 443063 pages, 8 passes, moved 395186 pages, stopping reasons bits 0x4, took 538.965 seconds, discontinued by user

$ ./mdbx_defrag -3 test-28MiBdat
mdbx_defrag v0.14.1-477-g051b7437 (2026-03-20T06:30:27+03:00, T-27b0aaea4bda4436bf8f7fad00661cca07368130)
Running for test-28MiB.dat...
 - space usage in pages: 1340931 allocated, payload 1331857, unused/GC 9074, pagesize 16384
 - defragmentation: target 100% (shrink 0 pages), cycles limit 3, step unlimited, duration unlimited
 - loading the b-tree structure: 99.9%........................................................... done
 - cycle 1: 100.0%, moved 4941, left 9074... large chunk
 - cycle 2: 100.0%, moved 3105, shrinked 4491, left 4583... done
 - cycle 3: 100.0%, moved 1217, shrinked 7377, left 1697... done
 - cycle 4: 0.0%, shrinked 7377, left 1697... discontinued by user
Defragmentation: shrinked 7377 pages, 4 passes, moved 9263 pages, stopping reasons bits 0x4, took 64.442 seconds, discontinued by user