This patch adds the MIR parsing and serialization support for save and
restore points with subsets of callee saved registers. That is, it
syntactically allows a function to contain two or more distinct
sub-regions in which distinct subsets of registers are spilled/filled as
callee save. This is useful if e.g. one of the CSRs isn't modified in
one of the sub-regions, but is in the other(s).

Support for actually using this capability in code generation is still
forthcoming. This patch is the next logical step for multiple
save/restore points support.

All points are now stored in DenseMap from MBB to vector of
CalleeSavedInfo.

Shrink-Wrap points split Part 4.
RFC:
https://discourse.llvm.org/t/shrink-wrap-save-restore-points-splitting/83581

Part 1: https://github.com/llvm/llvm-project/pull/117862 (landed)
Part 2: https://github.com/llvm/llvm-project/pull/119355 (landed)
Part 3: https://github.com/llvm/llvm-project/pull/119357 (landed)
Part 5: https://github.com/llvm/llvm-project/pull/119359 (likely to be
further split)

Remove the type alias now that the std::variant aspect is gone, directly
using std::vector in the few places that need it is more idiomatic.

Move a routine from a core header to single user.

In review of bbde6b, I had originally proposed that we support the
legacy text format. As review evolved, it bacame clear this had been a
bad idea (too much complexity), but in order to let that patch finally
move forward, I approved the change with the variant. This change undoes
the variant, and updates all the tests to just use the array form.

Currently mir supports only one save and one restore point
specification:

```
  savePoint:       '%bb.1'
  restorePoint:    '%bb.2'
```

This patch provide possibility to have multiple save and multiple
restore points in mir:

```
  savePoints:
    - point:           '%bb.1'
  restorePoints:
    - point:           '%bb.2'
```

Shrink-Wrap points split Part 3.
RFC:
https://discourse.llvm.org/t/shrink-wrap-save-restore-points-splitting/83581

Part 1: https://github.com/llvm/llvm-project/pull/117862
Part 2: https://github.com/llvm/llvm-project/pull/119355
Part 4: https://github.com/llvm/llvm-project/pull/119358
Part 5: https://github.com/llvm/llvm-project/pull/119359

peekDebugInstrNum() already returns unsigned.

This reverts commit 05e08cdb3e576cc0887d1507ebd2f756460c7db7.
Adding the missing -mtriple flags in MIR/X86 test files which caused
these tests to fail which was the reason for reverting the patch.

Reverts llvm/llvm-project#87574, which breaks LLVM ::
CodeGen/MIR/X86/call-site-info-ambiguous-indirect-call-typeid.mir tests
on linux-arm64 builders.

Introducing `EnableCallGraphSection` target option to add
CalleeTypeIds field in CallSiteInfo. Read the callee type ids
in and out by the MIR parser/printer.

Reviewers: ilovepi

Reviewed By: ilovepi

Pull Request: https://github.com/llvm/llvm-project/pull/87574

Add per-property has<Prop>/set<Prop>/reset<Prop> functions to
MachineFunctionProperties.