libafl_cc: gate unsupported custom passes on llvm 22

[terabyte-trifler]

Summary

• detect LLVM 22+ in libafl_cc and stop trying to build custom passes that are not yet known to be compatible there
• skip loading those unsupported passes at wrapper runtime with a clear diagnostic instead of failing the whole compiler-wrapper flow
• document the LLVM 22 support boundary in the libafl_cc README and add a unit test for the pass support matrix

Details

This keeps the maintained cmplog and autotokens pass flow working on newer LLVM releases while avoiding hard build failures from custom LibAFL-specific passes that still need to be ported.

On LLVM 22 and newer, this change skips:

• function-logging
• coverage-accounting
• ctx
• dump-cfg

Testing

• cargo test -p libafl_cc

Closes #3769.