PTX: Use LLVM 22 back-end from JLL.

[maleadt]

Because having to support Julia 1.10, shipping LLVM 15, is becoming a problem. With NVPTX at least there's a relatively clean split between the middle- and back-end, with most back-end passes being scheduled after the optimization pipeline (only AS inference and range intrinsic lowering is part of the middle-end). So we could simply use llc from a more modern LLVM version to generate PTX code.

One problem is probably going to be opaque pointers: LLVM 22 rejects them, while Julia 1.10 and 1.11 still use typed pointers by default.

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.55%. Comparing base (ef59201) to head (05cc909).

Files with missing lines	Patch %	Lines
src/ptx.jl	80.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #801      +/-   ##
==========================================
+ Coverage   75.05%   75.55%   +0.50%     
==========================================
  Files          25       25              
  Lines        3901     3895       -6     
==========================================
+ Hits         2928     2943      +15     
+ Misses        973      952      -21     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.