Add operators to shift left or right and insert unknown bits.

Closes #151043 
https://alive2.llvm.org/ce/z/JyMSk8

## 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

Changes are:
    1) Make signed-overflow detection optimal
    2) For signed-overflow, try to rule out direction even if we can't
       totally rule out overflow.
    3) Intersect add/sub assuming no overflow with possible overflow
       clamping values as opposed to add/sub without the assumption.

Rewrite the signed functions in terms of the unsigned ones which are
already optimal.

KnownBits::srem does not correctly set the leader zero-bits, omitting
the fact that LHS may be known-negative or known-non-negative. Fix this.

Alive2 proof: https://alive2.llvm.org/ce/z/Ugh-Dq

Use the internal computeForAddCarry directly since we know the exact values of the carry bit.

Allow KnownBits to represent "always poison" values via conflict.

close: #94436