[devtools] Extend language-C and language-CPP supported values

[EaselinkBachmann]

This PR adds the remaining missing C and C++ language standards to AC6, GCC, and CLANG.

• add C standards gnu17 and gnu23
• add C++ standards c++23 and gnu++23
• fix C++ standards c++20 and gnu++20 incorrectly setting -std=c++17 and -std=gnu++17 on AC6

Fixes #1785

[github-actions]

Test Results

  7 files   53 suites   4m 14s ⏱️
185 tests 168 ✅ 17 💤 0 ❌
692 runs  624 ✅ 68 💤 0 ❌

Results for commit da38061.

♻️ This comment has been updated with latest results.

[brondani]

LGTM

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.92%. Comparing base (2f01ab2) to head (da38061).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1799   +/-   ##
=======================================
  Coverage   64.92%   64.92%           
=======================================
  Files         163      163           
  Lines       34453    34453           
  Branches    19975    19975           
=======================================
  Hits        22367    22367           
- Misses       7900     7918   +18     
+ Partials     4186     4168   -18     

Flag	Coverage Δ
buildmgr-cov	73.94% <ø> (ø)
projmgr-cov	81.72% <ø> (ø)

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see 10 files with indirect coverage changes