This is a follow-up to #156140 and #160979, which deprecated one form of
write and read, respectively.

We have two forms of byte_swap:

  template <typename value_type>
[[nodiscard]] inline value_type byte_swap(value_type value, endianness
endian)

  template <typename value_type, endianness endian>
  [[nodiscard]] inline value_type byte_swap(value_type value)

The difference is that endian is a function parameter in the former
but a template parameter in the latter.

This patch streamlines the code by migrating the use of the latter to
the former while deprecating the latter because the latter is just
forwarded to the former.

Factor out code in `populateCounters()` and `populateCoverage()` used to
grab the record into `PGOUseFunc::getRecord()` to reduce code
duplication. And return `NamedInstrProfRecord` in `getInstrProfRecord()`
to avoid an unnecessary cast. No functional change is intented.

The InstrProf headers are very expensive. Avoid including them in all of
CodeGen/ by moving the CodeGenPGO member behind a unqiue_ptr.

This reduces clang build time by 0.8%.

This is an expensive header, only include it where needed. Move some
functions out of line to achieve that.

This reduces time to build clang by ~0.5% in terms of instructions
retired.

I'm adding support for SPIR-V, so let's consolidate these checks.

---------

Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>

This pull request is the third part of an ongoing effort to extends PGO
instrumentation to GPU device code and depends on
https://github.com/llvm/llvm-project/pull/93365. This PR makes the
following changes:

- Allows PGO flags to be supplied to GPU targets
- Pulls version global from device
- Modifies `__llvm_write_custom_profile` and `lprofWriteDataImpl` to
allow the PGO version to be overridden

`CounterPair` can hold `<uint32_t, uint32_t>` instead of current
`unsigned`, to hold also the counter number of SkipPath. For now, this
change provides the skeleton and only `CounterPair::Executed` is used.

Each counter number can have `None` to suppress emitting counter
increment. 2nd element `Skipped` is initialized as `None` by default,
since most `Stmt*` don't have a pair of counters.

This change also provides stubs for the verifier. I'll provide the impl
of verifier for `+Asserts` later.

`markStmtAsUsed(bool, Stmt*)` may be used to inform that other side
counter may not emitted.

`markStmtMaybeUsed(S)` may be used for the `Stmt` and its inner will be
excluded for emission in the case of skipping by constant folding. I put
it into places where I found.

`verifyCounterMap()` will check the coverage map and the counter map,
and can be used to report inconsistency.

These verifier methods shall be eliminated in `-Asserts`.


https://discourse.llvm.org/t/rfc-integrating-singlebytecoverage-with-branch-coverage/82492

Identified with misc-include-cleaner.