Stabilize MPI test timing

[aobolensk]

Synchronize ranks before timed sections so scheduler skew and barrier waits are not counted as task runtime, preventing rare timeout flakes like these:

[ RUN      ] PicMatrixTests/NesterovARunFuncTestsProcesses3.MatmulFromPic/nesterov_a_test_task_processes_3_mpi_enabled_3_3
unknown file: error: C++ exception with description "
Task execute time need to be: time < 1 secs.
Original time in secs: 1.21769
" thrown in the test body.

[       OK ] PicMatrixTests/NesterovARunFuncTestsProcesses3.MatmulFromPic/nesterov_a_test_task_processes_3_mpi_enabled_3_3 (1224 ms)
[  FAILED  ] PicMatrixTests/NesterovARunFuncTestsProcesses3.MatmulFromPic/nesterov_a_test_task_processes_3_mpi_enabled_3_3, where GetParam() = (64-byte object <20-AA 75-60 F6-7F 00-00 C0-6C 6E-60 F6-7F 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 88-77 B8-48 FD-01 00-00>, "nesterov_a_test_task_processes_3_mpi_enabled", (3, "3")) (1225 ms)
[ RUN      ] PicMatrixTests/NesterovARunFuncTestsProcesses3.MatmulFromPic/nesterov_a_test_task_processes_3_mpi_enabled_7_7

job aborted:
[ranks] message

[0] terminated

[1] application aborted
aborting MPI_COMM_WORLD (comm=0x44000000), error 1, comm rank 1

[2] terminated

---- error analysis -----

[1] on runnervmqq1k9
D:\a\parallel_programming_course\parallel_programming_course\install\bin\ppc_func_tests aborted the job. abort code 1

---- error analysis -----
 [  PROCESS 1  ]  [  PROCESS 1  ] Traceback (most recent call last):
  File "D:\a\parallel_programming_course\parallel_programming_course\scripts\run_tests.py", line 308, in <module>
    _execute(args_dict, env_copy)
  File "D:\a\parallel_programming_course\parallel_programming_course\scripts\run_tests.py", line 283, in _execute
    runner.run_processes(args_dict["additional_mpi_args"])
  File "D:\a\parallel_programming_course\parallel_programming_course\scripts\run_tests.py", line 247, in run_processes
    self.__run_exec(
  File "D:\a\parallel_programming_course\parallel_programming_course\scripts\run_tests.py", line 122, in __run_exec
    raise Exception(f"Subprocess return {result.returncode}.")
Exception: Subprocess return 1.
Error: Process completed with exit code 1.

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[codecov]

Codecov Report

❌ Patch coverage is 55.55556% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.13%. Comparing base (626e4be) to head (9bc57a2).

Files with missing lines	Patch %	Lines
modules/util/src/util.cpp	55.55%	1 Missing and 3 partials ⚠️

❌ Your patch check has failed because the patch coverage (55.55%) 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     #780      +/-   ##
==========================================
- Coverage   93.82%   93.13%   -0.70%     
==========================================
  Files          15       15              
  Lines         486      495       +9     
  Branches      182      180       -2     
==========================================
+ Hits          456      461       +5     
- Misses          0        1       +1     
- Partials       30       33       +3     

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