[fix] Stabilize MPI tests and prevent hangs

[allnes]

• Sync gtest random_seed + filter across ranks
• Abort on worker failure; wrap RunAllTests with MPI_Abort on exceptions
• Make PPC_TEST_TMPDIR per MPI rank
• Pass env to mpiexec on Windows (-env), keep -x on *nix

[codecov]

Codecov Report

❌ Patch coverage is 57.14286% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.03%. Comparing base (5d9ac5d) to head (8a47148).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
modules/util/include/util.hpp	57.14%	0 Missing and 3 partials ⚠️

❌ Your patch status has failed because the patch coverage (57.14%) is below the target coverage (95.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #672      +/-   ##
==========================================
- Coverage   94.58%   94.03%   -0.56%     
==========================================
  Files          15       15              
  Lines         480      486       +6     
  Branches      177      181       +4     
==========================================
+ Hits          454      457       +3     
- Partials       26       29       +3     

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