[ThinLTO][TypeProf] Implement vtable def import (#79381)

Add annotated vtable GUID as referenced variables in per function
summary, and update bitcode writer to create value-ids for these
referenced vtables.

- This is the part3 of type profiling work, and described in the "Virtual Table Definition Import" [1] section of the
RFC.

[1] https://github.com/llvm/llvm-project/pull/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