test: #18574: fix threading workaround

[akugal]

Description: Some timing sensitive tests may fail, because previous test might have created huge virtual map and copies, that have not yet been fully disposed by asinc VirtualPipeline thread, causing OOM errors. When dealing with huge virtual maps in tests, ensure in the end that map and copies have been released and wait on VirtualPipeline termination.

Fixes #18574

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

@@                         Coverage Diff                         @@
##             18574-fix-workaround-map-release   #18885   +/-   ##
===================================================================
  Coverage                                    ?   69.44%           
  Complexity                                  ?    23146           
===================================================================
  Files                                       ?     2629           
  Lines                                       ?   100039           
  Branches                                    ?    10339           
===================================================================
  Hits                                        ?    69475           
  Misses                                      ?    26607           
  Partials                                    ?     3957           

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