[clang] [clang][ssaf] Add EntityLinkage support to TUSummaryBuilder and CallGraphExtractor (PR #194448)

[Balázs Benics via cfe-commits]

steakhal wrote:

Ah, I just realised that I have squashed the change where I keep reserving the EntityId 0, and start handing IDs out starting with 1.

I could probably split it if you think I should.

https://github.com/llvm/llvm-project/pull/194448