[Serialization] Add ModuleSummary serialization format

[kateinoigakukun]

This will be unblocked when #33324 merged.

This PR adds the actual serialization and deserialization implementation of module summary which will be used for cross dead function elimination.

The module summary file consists of function summaries and virtual function tables.

Function Summary

A function summary has a globally unique identifier and function call info. The function call info indicates how the callee function is referenced (e.g. witness_method, class_method or function_ref).

Virtual Function Table

A virtual function table has a map of virtual method to implementations.

protocol P {
  func foo1()
}

struct S1: P {
  func foo1() {}
}
struct S2: P {
  func foo1() {}
}

For example, this code will be summarized into

witness_tables:
  P.foo1:
    - S1.foo1
    - S2.foo2

For more info: https://forums.swift.org/t/refactoring-plan-of-silvisitor-for-lto/37678/14

CC: @compnerd @gottesmm

[MaxDesiatov]

@swift-ci please smoke test

[MaxDesiatov]

@swift-ci please smoke test

[kateinoigakukun]

Finally, CI passed

[MaxDesiatov]

@compnerd @gottesmm would you be able to have a look at this please?

[kateinoigakukun]

Close as it's too stale for now.