[csolution-rpc] Handle GetDraftProjects method

[grasci-arm]

Implement Open-CMSIS-Pack/csolution-rpc#24
Partly address ARM-software/vscode-cmsis-csolution#284

[github-actions]

Test Results

    3 files     21 suites   13m 30s ⏱️
  418 tests   418 ✅ 0 💤 0 ❌
1 254 runs  1 254 ✅ 0 💤 0 ❌

Results for commit 3169a86.

[codecov]

Codecov Report

❌ Patch coverage is 72.29730% with 41 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.60%. Comparing base (963c817) to head (3169a86).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
tools/projmgr/test/src/ProjMgrRpcTests.cpp	50.98%	0 Missing and 25 partials ⚠️
tools/projmgr/src/ProjMgrRpcServer.cpp	87.87%	2 Missing and 6 partials ⚠️
tools/projmgr/include/ProjMgrWorker.h	16.66%	4 Missing and 1 partial ⚠️
tools/projmgr/src/ProjMgrWorker.cpp	88.00%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2166      +/-   ##
==========================================
+ Coverage   66.58%   66.60%   +0.01%     
==========================================
  Files         181      181              
  Lines       38243    38377     +134     
  Branches    22375    22483     +108     
==========================================
+ Hits        25464    25560      +96     
- Misses       8076     8082       +6     
- Partials     4703     4735      +32     

Flag	Coverage Δ
projmgr-cov	80.81% <72.29%> (-0.08%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
tools/projmgr/src/ProjMgrWorker.cpp	87.83% <88.00%> (+0.03%)	⬆️
tools/projmgr/include/ProjMgrWorker.h	64.28% <16.66%> (-12.99%)	⬇️
tools/projmgr/src/ProjMgrRpcServer.cpp	66.19% <87.87%> (+3.97%)	⬆️
tools/projmgr/test/src/ProjMgrRpcTests.cpp	56.15% <50.98%> (-0.57%)	⬇️

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