[projmgr] Skip processing candidate layers during detection phase

[spcaipers-arm]

Address #1841 and #1850

[github-actions]

Test Results

    3 files     18 suites   8m 15s ⏱️
  376 tests   376 ✅ 0 💤 0 ❌
1 128 runs  1 128 ✅ 0 💤 0 ❌

Results for commit 94f1055.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.

Project coverage is 64.96%. Comparing base (8422a81) to head (94f1055).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
tools/projmgr/src/ProjMgrWorker.cpp	0.00%	2 Missing and 3 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1875   +/-   ##
=======================================
  Coverage   64.96%   64.96%           
=======================================
  Files         163      163           
  Lines       34587    34564   -23     
  Branches    20065    20052   -13     
=======================================
- Hits        22468    22455   -13     
+ Misses       7960     7955    -5     
+ Partials     4159     4154    -5     

Flag	Coverage Δ
projmgr-cov	81.71% <0.00%> (+0.04%)	⬆️

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	87.90% <0.00%> (+0.20%)	⬆️