This implements the result of the discussion at:

https://discourse.llvm.org/t/rfc-report-fatal-error-and-the-default-value-of-gencrashdialog/73587

There are two different use cases for report_fatal_error, so replace it
with two functions reportFatalInternalError() and
reportFatalUsageError(). The former indicates a bug in LLVM and
generates a crash dialog. The latter does not. The names have been
suggested by rnk and people seemed to like them.

This replaces a lot of the usages that passed an explicit value for
GenCrashDiag. I did not bulk replace remaining report_fatal_error usage
-- they probably require case by case review for which function to use.

This is needed in llvm-reduce to avoid perturbing the uselistorder in
intermediate steps. Really llvm-reduce wants pure serialization with
no dependency on the pass manager. There are other optimizations mixed
in to the serialization here depending on metadata in the module, which
is also bad.
    
Part of #63621

After https://github.com/llvm/llvm-project/pull/131217 was submitted,
time-passes.ll fails because `opt` prints `-time-report` when
`ManagedTimerGlobals` is destroyed. `ManagedTimerGlobals` stores
`TimerGroup`s in an unordered map, so the ordering of the output
`TimerGroup`s depends on the underlying iterator.

To fix this, we do what Clang does and use
`llvm::TimerGroup::printAll(...)`, which *is* deterministic. This is
also what Clang does. This does put move analysis section before the
pass section for `-time-report`, but again, this is also what Clang
currently does.

These date back to when the non-intrinsic format of variable locations
was still being tested and was behind a compile-time flag, so not all
builds / bots would correctly run them. The solution at the time, to get
at least some test coverage, was to have tests opt-in to non-intrinsic
debug-info if it was built into LLVM.

Nowadays, non-intrinsic format is the default and has been on for more
than a year, there's no need for this flag to exist.

(I've downgraded the flag from "try" to explicitly requesting
non-intrinsic format in some places, so that we can deal with tests that
are explicitly about non-intrinsic format in their own commit).

This is meant as a preparation for PR #130988 "[AMDGPU] Implement IR
expansion for frem instruction" which implements the expansion of
another instruction in this pass. The more general name seems more
appropriate given this change and quite reasonable even without it.

The module currently stores the target triple as a string. This means
that any code that wants to actually use the triple first has to
instantiate a Triple, which is somewhat expensive. The change in #121652
caused a moderate compile-time regression due to this. While it would be
easy enough to work around, I think that architecturally, it makes more
sense to store the parsed Triple in the module, so that it can always be
directly queried.

For this change, I've opted not to add any magic conversions between
std::string and Triple for backwards-compatibilty purses, and instead
write out needed Triple()s or str()s explicitly. This is because I think
a decent number of them should be changed to work on Triple as well, to
avoid unnecessary conversions back and forth.

The only interesting part in this patch is that the default triple is
Triple("") instead of Triple() to preserve existing behavior. The former
defaults to using the ELF object format instead of unknown object
format. We should fix that as well.

Added an extension point after vectorizer passes in the PassBuilder.
Additionally, added extension points before and after vectorizer passes
in `buildLTODefaultPipeline`. Credit goes to @mshockwave for guiding me
through my first LLVM contribution (and my first open source
contribution in general!) :)
- Implemented `registerVectorizerEndEPCallback`
- Implemented `invokeVectorizerEndEPCallbacks`
- Added `VectorizerEndEPCallbacks` SmallVector
- Added a command line option `passes-ep-vectorizer-end` to
`NewPMDriver.cpp`
- `buildModuleOptimizationPipeline` now calls
`invokeVectorizerEndEPCallbacks`
- `buildO0DefaultPipeline` now calls `invokeVectorizerEndEPCallbacks`
- `buildLTODefaultPipeline` now calls BOTH
`invokeVectorizerStartEPCallbacks` and `invokeVectorizerEndEPCallbacks`
- Added LIT tests to `new-pm-defaults.ll`, `new-pm-lto-defaults.ll`,
`new-pm-O0-ep-callbacks.ll`, and `pass-pipeline-parsing.ll`
- Renamed `CHECK-EP-Peephole` to `CHECK-EP-PEEPHOLE` in
`new-pm-lto-defaults.ll` for consistency.

This code is intended for developers that wish to implement and run
custom passes after the vectorizer passes in the PassBuilder pipeline.
For example, in #91796, a pass was created that changed the induction
variables of vectorized code. This is right after the vectorization
passes.

Following discussions in #110443, and the following earlier discussions
in https://lists.llvm.org/pipermail/llvm-dev/2017-October/117907.html,
https://reviews.llvm.org/D38482, https://reviews.llvm.org/D38489, this
PR attempts to overhaul the `TargetMachine` and `LLVMTargetMachine`
interface classes. More specifically:
1. Makes `TargetMachine` the only class implemented under
`TargetMachine.h` in the `Target` library.
2. `TargetMachine` contains target-specific interface functions that
relate to IR/CodeGen/MC constructs, whereas before (at least on paper)
it was supposed to have only IR/MC constructs. Any Target that doesn't
want to use the independent code generator simply does not implement
them, and returns either `false` or `nullptr`.
3. Renames `LLVMTargetMachine` to `CodeGenCommonTMImpl`. This renaming
aims to make the purpose of `LLVMTargetMachine` clearer. Its interface
was moved under the CodeGen library, to further emphasis its usage in
Targets that use CodeGen directly.
4. Makes `TargetMachine` the only interface used across LLVM and its
projects. With these changes, `CodeGenCommonTMImpl` is simply a set of
shared function implementations of `TargetMachine`, and CodeGen users
don't need to static cast to `LLVMTargetMachine` every time they need a
CodeGen-specific feature of the `TargetMachine`.
5. More importantly, does not change any requirements regarding library
linking.

cc @arsenm @aeubanks