Tracking LLVM removal blockers for future LLVM deprecations

[elliottslaughter]

This is a tracking issue for hypothetical, currently unplanned removal of LLVM versions > 10. Like #543 I'm doing this very early so that we get a sense of what's holding us back in terms of dropping older LLVM versions. No specific deprecations are planned at this time.

As far as I know, the following blockers are currently holding us back:

• Windows: requires LLVM <= 11, see Windows: LLVM 12+ fail in JIT #540
• Linux ARM: requires LLVM <= 11, see AArch64 Linux test failures on LLVM 12 and newer #597
• AMD GPU: requires LLVM <= 15, see Regent: ROCm/LLVM compatibility and support tracking issue StanfordLegion/legion#1526
• LLVM 17 issues (if we set the bound to LLVM 17 or higher): Known issues in LLVM 17 #655
• setinlined not working in JIT mode on LLVM >= 17 #671

I will update this issue as subsequent blockers come up.