RUM-3757: Make sure error.threads always have content from error.stack

[0xnm]

What does this PR do?

It seems sometimes it is possible to have result of Thread.getAllStackTraces() without the thread impacted by ANR/crashing thread info (or without attached stacktrace, not sure here). It is not clear why it happens, but we clearly can see such issues in the dashboard, when error.stack is not found among error.threads reported (meaning error.threads doesn't have thread for which we reporting error.stack).

This change fixes that by making sure ANR thread/crashing thread is always in the error.threads - we will always add it to the list, not relying on the match among Thread.getAllStackTraces() results.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

Merging #1964 (dac8d88) into develop (fb5a1de) will increase coverage by 0.07%.
The diff coverage is 96.30%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1964      +/-   ##
===========================================
+ Coverage    83.31%   83.38%   +0.07%     
===========================================
  Files          489      489              
  Lines        17883    17880       -3     
  Branches      2666     2663       -3     
===========================================
+ Hits         14899    14909      +10     
+ Misses        2240     2234       -6     
+ Partials       744      737       -7     

Files	Coverage Δ
...og/android/rum/internal/anr/ANRDetectorRunnable.kt	80.70% <100.00%> (+1.07%)	⬆️
.../android/error/internal/DatadogExceptionHandler.kt	87.84% <94.44%> (+0.69%)	⬆️

... and 30 files with indirect coverage changes