Remove parallel test execution and mark long tests

[AndreKurait]

Description

We're seeing some intermittent test failures during parallel execution due. While we would like to make the tests robust to these timing differences, for the maturity of the project and for the meantime, seeking to disable parallel test execution.

Also, marked some long running tests (> 2s per run) as longTest

• Category: Enhancement
• Why these changes are required? Test Reliablity
• What is the old behavior before changes and new behavior after changes? Tests would intermittently fail, now tests take ~30 seconds and run reliably

Issues Resolved

MIGRATIONS-1666

Is this a backport? If so, please add backport PR # and/or commits #

Testing

Ran on M1 Pro macbook, got build and test execution down to 29s https://gradle.com/s/6sybg3hsa6lry

Check List

• [x ] New functionality includes testing
  • [x ] All tests pass, including unit test, integration test and doctest
• New functionality has been documented
• [ x] Commits are signed per the DCO using --signoff

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.96%. Comparing base (2b853a9) to head (90b91f2).
Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #588      +/-   ##
============================================
+ Coverage     75.74%   75.96%   +0.22%     
+ Complexity     1495     1492       -3     
============================================
  Files           162      162              
  Lines          6348     6348              
  Branches        572      572              
============================================
+ Hits           4808     4822      +14     
+ Misses         1160     1147      -13     
+ Partials        380      379       -1     

Flag	Coverage Δ
unittests	75.96% <ø> (+0.22%)	⬆️

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[gregschohn]

lgtm. thx!