Basic process mem usage functions

[DmitriyMusatkin]

Issue #, if available:

Description of changes:

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[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (f705c61) 82.69% compared to head (31624a6) 82.68%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1065      +/-   ##
==========================================
- Coverage   82.69%   82.68%   -0.02%     
==========================================
  Files          54       55       +1     
  Lines        5708     5716       +8     
==========================================
+ Hits         4720     4726       +6     
- Misses        988      990       +2     

Files	Coverage Δ
source/posix/system_resource_utils.c	87.50% <87.50%> (ø)

... and 1 file with indirect coverage changes

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[waahm7]

Debatable: We already have a system_info header which might be a good place for these functions.

[DmitriyMusatkin]

Im on the fence about it. I was originally planning to put it into system_info, but functions here have a slightly different use case - how many resource is my process consuming vs which system im running on. I was also planning to add functions to modify resource limits to this file, which will diverge things even more in future. So im leaning towards a separate header.