Bugfix: Shmem array binary search test

[Davknapp]

Closes #1726

adds a test for the shmem binary search.
Initializes a shared memory array where each entry is set to its index.
Then searches for each index and compares for equality.
Additionally searches for values outside of the range to check if -1 is returned.
Found an error and fixed it.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.42%. Comparing base (d4a8b44) to head (99fb7a5).
⚠️ Report is 19 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2114   +/-   ##
=======================================
  Coverage   77.41%   77.42%           
=======================================
  Files         113      113           
  Lines       19178    19178           
=======================================
+ Hits        14847    14848    +1     
+ Misses       4331     4330    -1     

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[holke]

Cool addition. Looks good up to minor corrections.