[SampleFDO][TypeProf]Support vtable type profiling for ext-binary and text format (#148002)

This change extends SampleFDO ext-binary and text format to record the
vtable symbols and their counts for virtual calls inside a function. The
vtable profiles will allow the compiler to annotate vtable types on IR
instructions and perform vtable-based indirect call promotion. An RFC is
in
https://discourse.llvm.org/t/rfc-vtable-type-profiling-for-samplefdo/87283

Given a function below, the before vs after of a function's profile is
illustrated in text format in the table:

```
__attribute__((noinline)) int loop_func(int i, int a, int b) {
    Base *ptr = createType(i);

    int sum = ptr->func(a, b);
    
    delete ptr;
    
    return sum;
}
```

| before | after |
| --- | --- |
| Samples collected in the function's body { <br> 0: 636241 <br> 1:
681458, calls: _Z10createTypei:681458 <br> 3: 543499, calls:
_ZN12_GLOBAL__N_18Derived24funcEii:410621 _ZN8Derived14funcEii:132878
<br> 5.1: 602201, calls: _ZN12_GLOBAL__N_18Derived2D0Ev:454635
_ZN8Derived1D0Ev:147566 <br> 7: 511057 <br> } | Samples collected in the
function's body { <br> 0: 636241 <br> 1: 681458, calls:
_Z10createTypei:681458 <br> 3: 543499, calls:
_ZN12_GLOBAL__N_18Derived24funcEii:410621 _ZN8Derived14funcEii:132878
<br> 3: vtables: _ZTV8Derived1:1377 _ZTVN12_GLOBAL__N_18Derived2E:4250
<br> 5.1: 602201, calls: _ZN12_GLOBAL__N_18Derived2D0Ev:454635
_ZN8Derived1D0Ev:147566 <br> 5.1: vtables: _ZTV8Derived1:227
_ZTVN12_GLOBAL__N_18Derived2E:765 <br> 7: 511057 <br> } |

Key points for this change:
1. In-memory representation of vtable profiles
* A field of type `map<LineLocation, map<FunctionId, uint64_t>>` is
introduced in a function's in-memory representation
[FunctionSamples](https://github.com/llvm/llvm-project/blob/ccc416312ed72e92a885425d9cb9c01f9afa58eb/llvm/include/llvm/ProfileData/SampleProf.h#L749-L754).
2. The vtable counters for one LineLocation represents the relative
frequency among vtables for this LineLocation. They are not required to
be comparable across LineLocations.
3. For backward compatibility of ext-binary format, we take one bit from
ProfSummaryFlag as illustrated in the enum class `SecProfSummaryFlags`.
The ext-binary profile reader parses the integer type flag and reads
this bit. If it's set, the profile reader will parse vtable profiles.
4. The vtable profiles are optional in ext-binary format, and not
serialized out by default, we introduce an LLVM boolean option (named
`-extbinary-write-vtable-type-prof`). The ext-binary profile writer
reads the boolean option and decide whether to set the section flag bit
and serialize the in-memory class members corresponding to vtables.
5. This change doesn't implement `llvm-profdata overlap --sample` for
the vtable profiles. A subsequent change will do it to keep this one
focused on the profile format change.

We don't plan to add the vtable support to non-extensible format mainly
because of the maintenance cost to keep backward compatibility for prior
versions of profile data.
* Currently, the [non-extensible binary
format](https://github.com/llvm/llvm-project/blob/5c28af409978c19a35021855a29dcaa65e95da00/llvm/lib/ProfileData/SampleProfWriter.cpp#L899-L900)
does not have feature parity with extensible binary format today, for
instance, the former doesn't support [profile symbol
list](https://github.com/llvm/llvm-project/blob/41e22aa31b1905aa3e9d83c0343a96ec0d5187ec/llvm/include/llvm/ProfileData/SampleProf.h#L1518-L1522)
or context-sensitive PGO, both of which give measurable performance
boost. Presumably the non-extensible format is not in wide use.

---------

Co-authored-by: Paschalis Mpeis <paschalis.mpeis@arm.com>

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