[clang] [llvm] [SPIRV][RFC] Rework / extend support for memory scopes (PR #106429)

[Alex Voicu via cfe-commits]

AlexVlx wrote:

> @AlexVlx I don't see much objections against #108528 on a conceptual level, so what do you think about merging it into this PR in a way that I commented above, by changing `getMemScope()` and moving `getOrInsertSyncScopeID()` into its static vars initialization?

At a glance it seems fine, thank you for working through this, but since I've been away for a couple of days let me page things back in first:)

https://github.com/llvm/llvm-project/pull/106429