[llvm] [NFC][SPIRV] Re-work extension parsing (PR #171826)

[Mikael Holmen via llvm-commits]

https://github.com/mikaelholmen commented:

I have verified that the 143 lit tests that previously failed with expensive checks when built with gcc now pass with this patch, since the bad sort comparison has been reviewed so that looks good.
But I can't really review the actual code changes since I don't know this at all.

https://github.com/llvm/llvm-project/pull/171826