## Purpose
Add proper preprocessor guards for all `dump()` methods in the LLVM
support library. This change ensures these methods are not part of the
public ABI for release builds.

## Overview
* Annotates all `dump` methods in Support and ADT source with the
`LLVM_DUMP_METHOD` macro.
* Conditionally includes all `dump` method definitions in Support and
ADT source so they are only present on debug/assert builds and when
`LLVM_ENABLE_DUMP` is explicitly defined.

NOTE: For many of these `dump` methods, the implementation was already
properly guarded but the declaration in the header file was not.

## Background
This PR is a redo of #139804 with some changes to fix clang and unit
test build breaks.

This issue was raised in comments on #136629. I am addressing it as a
separate change since it is independent from the changes being made in
that PR.

According to [this
documentation](https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/Support/Compiler.h#L637),
`dump` methods should be annotated with `LLVM_DUMP_METHOD` and
conditionally included as follows:
```
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  LLVM_DUMP_METHOD void dump() const;
#endif
```

## Validation
* Local release build succeeds.
* CI

Reverts llvm/llvm-project#139804

## Purpose
Add proper preprocessor guards for all `dump()` methods in the LLVM
support library. This change ensures these methods are not part of the
public ABI for release builds.

## Overview
* Annotates all `dump` methods in Support and ADT source with the
`LLVM_DUMP_METHOD` macro.
* Conditionally includes all `dump` method definitions in Support and
ADT source so they are only present on debug/assert builds and when
`LLVM_ENABLE_DUMP` is explicitly defined.

NOTE: For many of these `dump` methods, the implementation was already
properly guarded but the declaration in the header file was not.

## Background
This issue was raised in comments on #136629. I am addressing it as a
separate change since it is independent from the changes being made in
that PR.

According to [this
documentation](https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/Support/Compiler.h#L637),
`dump` methods should be annotated with `LLVM_DUMP_METHOD` and
conditionally included as follows:
```
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  LLVM_DUMP_METHOD void dump() const;
#endif
```

## Validation
* Local release build succeeds.
* CI

FixedPointSemantics is exactly 32bits and this static_assert'ed after
its declaration. Add support for converting it to and from a uint32_t.

This defines the builtin macros specified in `7.18a.3 Precision macros`
of ISO/IEC TR 18037:2008. These are the `__*__` versions of them and the
formal definitions in stdfix.h can use them.

Prior to this patch FixedPointSemantics and APFixedPoint only support semantics where
the Scale larger or equal to zero and the Width is larger or equal to the Scale.
This patch removes both those requirements while staying API compatible.

Interestingly, MathExtras.h doesn't use <cmath> declaration, so move it out of
that header and include it when needed.

No functional change intended, but there's no longer a transitive include
fromMathExtras.h to cmath.

Most clients only used these methods because they wanted to be able to
extend or truncate to the same bit width (which is a no-op). Now that
the standard zext, sext and trunc allow this, there is no reason to use
the OrSelf versions.

The OrSelf versions additionally have the strange behaviour of allowing
extending to a *smaller* width, or truncating to a *larger* width, which
are also treated as no-ops. A small amount of client code relied on this
(ConstantRange::castOp and MicrosoftCXXNameMangler::mangleNumber) and
needed rewriting.

Differential Revision: https://reviews.llvm.org/D125557

Stop using APInt constructors and methods that were soft-deprecated in
D109483. This fixes all the uses I found in llvm, except for the APInt
unit tests which should still test the deprecated methods.

Differential Revision: https://reviews.llvm.org/D110807