[llvm] CodeGen: Eliminate dynamic relocations in the register superclass tables. (PR #119122)

[Owen Anderson via llvm-commits]

resistor wrote:

> No specific objection to this patch, but it seems like it could still be cleaned up. If we're storing the size of the list then why do we also need a sentinel value? I'd also be inclined to make `superclasses()` return an `ArrayRef` instead of `iterator_range` (but maybe that's just my own personal prejudice against unnecessary iterators).

Done.

https://github.com/llvm/llvm-project/pull/119122