[NFC] In InstrProf, generalize helper functions to take 'GlobalObject'. They...

[NFC] In InstrProf, generalize helper functions to take 'GlobalObject'. They currently take 'Functions' as function parameters or have 'Func' in the name. (#70287)

- For instance, `collectPGOFuncNameStrings` is reused a lot in https://github.com/llvm/llvm-project/pull/66825 to get the compressed vtable names; and in some added callsites it's just confusing to see 'func' since context clearly shows it's not. This function currently just takes a list of strings as input so name it to `collectGlobalObjectNameStrings`
- Do the rename in a standalone patch since the method is used in non-llvm codebase. It's easier to rollback this NFC in case rename in that codebase takes longer.