[Resources.Process] Replace .NET 6 target with .NET 8 and add .NET Standard 2.0 target

[joegoldman2]

Changes

Replace .NET 6 target, which will be very soon out of support, with .NET 8 and add support for .NET Standard 2.0.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (71655ce) to head (dd77c01).
Report is 496 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##             main     #2170       +/-   ##
============================================
+ Coverage   73.91%   100.00%   +26.08%     
============================================
  Files         267         2      -265     
  Lines        9615        14     -9601     
============================================
- Hits         7107        14     -7093     
+ Misses       2508         0     -2508     

Flag	Coverage Δ
unittests-Resources.Process	100.00% <ø> (?)

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see 266 files with indirect coverage changes