CI Optimization and Test Modernization

[ahueck]

• CI: improve runtime by using std::map instead of Abseil and streamlining the external benchmark matrix (LLVM 14, 18, 22).
• Test suite: more support of LLVM versions (14 through 22) specifically w.r.t. the transition to opaque pointers.

[coveralls]

Coverage Report for CI Build 27348755313

Coverage increased (+0.04%) to 89.879%

Details

• Coverage increased (+0.04%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	5681
Covered Lines:	5106
Line Coverage:	89.88%
Coverage Strength:	47720.98 hits per line

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💛 - Coveralls