[llvm] [MC] Rename getPrivateGlobalPrefix to getInternalSymbolPrefix. NFC (PR #185164)

[Alexis Engelke via llvm-commits]

https://github.com/aengelke commented:

What is the naming plan for PrivateLabelPrefix and LinkerPrivateGlobalPrefix?

I always interpreted PrivateGlobalPrefix as the prefix for globals that have `private` linkage in LLVM IR and from that PoV, this change is replacing one inconsistency with another.

https://github.com/llvm/llvm-project/pull/185164