Fix spawner tests timeout on source builds (backport #1692)

[mergify]

As reported by @christophfroehlich in #1685, it seems that spawner tests are inconsistent and timing out after some time. I was able to reproduce it locally and upon checking it seems like the CM's internal mutexes are blcoking as there is no ControllerManagerRunner in some of these tests. Adding these should fix the above timeout issues. I've tested it locally and it seems to work

Fixes #1685

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This is an automatic backport of pull request #1692 done by Mergify.

[mergify]

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	both modified:   controller_manager/test/test_spawner_unspawner.cpp

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.31%. Comparing base (c04a16f) to head (349e2ac).
Report is 30 commits behind head on humble.

Additional details and impacted files

@@             Coverage Diff             @@
##           humble    #1697       +/-   ##
===========================================
- Coverage   87.00%   62.31%   -24.70%     
===========================================
  Files          97      105        +8     
  Lines        7505    11319     +3814     
  Branches      677     7933     +7256     
===========================================
+ Hits         6530     7053      +523     
- Misses        688      807      +119     
- Partials      287     3459     +3172     

Flag	Coverage Δ
unittests	62.31% <100.00%> (-24.70%)	⬇️

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

Files with missing lines	Coverage Δ
controller_manager/test/test_spawner_unspawner.cpp	59.01% <100.00%> (-39.45%)	⬇️

... and 69 files with indirect coverage changes