Fix build issue on Windows.

issue:#73085

@maksfb PTAL thank you

* Place types and functions in the llvm::codelayout namespace
* Change EdgeCountT from pair<pair<uint64_t, uint64_t>, uint64_t> to a struct and utilize structured bindings.
  It is not conventional to use the "T" suffix for structure types.
* Remove a redundant copy in ChainT::merge.
* Change {ExtTSPImpl,CDSortImpl}::run to use return value instead of an output parameter
* Rename applyCDSLayout to computeCacheDirectedLayout: (a) avoid rare
  abbreviation "CDS" (cache-directed sort) (b) "compute" is more conventional
  for the specific use case
* Change the parameter types from std::vector to ArrayRef so that
  SmallVector arguments can be used.
* Similarly, rename applyExtTspLayout to computeExtTspLayout.

Reviewed By: Amir

Differential Revision: https://reviews.llvm.org/D159526

After BOLT's merge to LLVM, there are two (almost identical) versions of the
code layout algorithm. The diff unifies the implementations by keeping the one
in LLVM.

There are mild changes in the resulting block orders. I tested the changes
extensively both on the clang binary and on prod services. Didn't see stat sig
differences on average.

Reviewed By: Amir

Differential Revision: https://reviews.llvm.org/D129895

A const-qualified reference to function layout allows accessing
non-const qualified basic blocks on a const-qualified function. This
patch adds or removes const-qualifiers where necessary to indicate where
basic blocks are used in a non-const manner.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D132049

This reverts commit 587d2653420d75ef10f30bd612d86f1e08fe9ea7.

A const-qualified reference to function layout allows accessing
non-const qualified basic blocks on a const-qualified function. This
patch adds or removes const-qualifiers where necessary to indicate where
basic blocks are used in a non-const manner.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D132049

Identified with readability-redundant-control-flow.

This patch adds a dedicated class to keep track of each function's
layout. It also lays the groundwork for splitting functions into
multiple fragments (as opposed to a strict hot/cold split).

Reviewed By: maksfb

Differential Revision: https://reviews.llvm.org/D129518

Replace `std::` algorithms taking begin/end iterators with `llvm::` counterparts
accepting ranges.

Reviewed By: rafauler

Differential Revision: https://reviews.llvm.org/D128154