Similar to FindLastIV, add FindFirstIVSMin to support select (icmp(), x, y)
reductions where one of x or y is a decreasing induction, producing a SMin
 reduction. It uses signed max as sentinel value.

PR: https://github.com/llvm/llvm-project/pull/140451

Split the FindLastIV RecurKind into SMax and UMax variants, depending on
the reduction op produced.

The use of VectorBuilder here was simply obscuring what was actually
going on. For vp.load and vp.store, the resulting code is significantly
more idiomatic. For the vp.reduce cases, we remove several layers of
indirection, including passing parameters via implicit state on the
builder. In both cases, the code is significantly easier to follow.

Specifically this is the assertion in BasicBlock.cpp. Now that we're not
examining or setting that flag consistently (because it'll be deleted in
about an hour) there's no need to keep this assertion.

Original commit title:

[DebugInfo][RemoveDIs] Remove some debug intrinsic-only codepaths (#143451)

This reverts commit c71a2e688828ab3ede4fb54168a674ff68396f61.

/me squints -- this is hitting an assertion I thought had been deleted,
will revert and investigate for a bit.

These are opportunistic deletions as more places that make use of the
IsNewDbgInfoFormat flag are removed. It should (TM)(R) all be dead code
now that `IsNewDbgInfoFormat` should be true everywhere.

FastISel: we don't need to do debug-aware instruction counting any more,
because there are no debug instructions,
Autoupgrade: you can no-longer avoid autoupgrading of intrinsics to
records
DIBuilder: Delete the code for creating debug intrinsics (!)
LoopUtils: No need to handle debug instructions, they don't exist

## Purpose

This patch is one in a series of code-mods that annotate LLVM’s public
interface for export. This patch annotates the `llvm/Transforms`
library. These annotations currently have no meaningful impact on the
LLVM build; however, they are a prerequisite to support an LLVM Windows
DLL (shared library) build.

## Background

This effort is tracked in #109483. Additional context is provided in
[this
discourse](https://discourse.llvm.org/t/psa-annotating-llvm-public-interface/85307),
and documentation for `LLVM_ABI` and related annotations is found in the
LLVM repo
[here](https://github.com/llvm/llvm-project/blob/main/llvm/docs/InterfaceExportAnnotations.rst).

The bulk of these changes were generated automatically using the
[Interface Definition Scanner (IDS)](https://github.com/compnerd/ids)
tool, followed formatting with `git clang-format`.

The following manual adjustments were also applied after running IDS on
Linux:
- Removed a redundant `operator<<` from Attributor.h. IDS only
auto-annotates the 1st declaration, and the 2nd declaration being
un-annotated resulted in an "inconsistent linkage" error on Windows when
building LLVM as a DLL.
- `#include` the `VirtualFileSystem.h` in PGOInstrumentation.h and
remove the local declaration of the `vfs::FileSystem` class. This is
required because exporting the `PGOInstrumentationUse` constructor
requires the class be fully defined because it is used by an argument.
- Add #include "llvm/Support/Compiler.h" to files where it was not
auto-added by IDS due to no pre-existing block of include statements.
- Add `LLVM_TEMPLATE_ABI` and `LLVM_EXPORT_TEMPLATE` to exported
instantiated templates.

## Validation

Local builds and tests to validate cross-platform compatibility. This
included llvm, clang, and lldb on the following configurations:

- Windows with MSVC
- Windows with Clang
- Linux with GCC
- Linux with Clang
- Darwin with Clang

Now that there is only a single FindLastIV recurrence kind, simply pass
the sentinel value instead of the full recurrence descriptor to tighten
the interface.

Now that there is only a single AnyOf recurrence kind, simply pass the
start value instead of the full recurrence descriptor, to tighten the
interface.

Add a new reduction recurrence kind for reductions with
minimumnum/maximumnum. Such reductions can be vectorized without
nsz/nnans, same as reductions with maximum/minimum intrinsics.

Note that a new reduction kind is needed to make sure partial reductions
are also combined with minimumnum/maximumnum.

Note that the final reduction to a scalar value is performed with
vector.reduce.fmin/fmax. This should be fine, as the results of the
partial reductions with maximumnum/minimumnum silences any sNaNs.

In-loop and reductions in SLP are not supported yet, as there's no
reduction version of maximumnum/minimumnum yet and fmax may be
incorrect.

PR: https://github.com/llvm/llvm-project/pull/137335