This adds WebAssembly support for the new [Lime1 CPU].

First, this defines some new target features. These are subsets of
existing
features that reflect implementation concerns:

- "call-indirect-overlong" - implied by "reference-types"; just the
overlong
encoding for the `call_indirect` immediate, and not the actual reference
   types.

 - "bulk-memory-opt" - implied by "bulk-memory": just `memory.copy` and
   `memory.fill`, and not the other instructions in the bulk-memory
    proposal.

Next, this defines a new target CPU, "lime1", which enables
mutable-globals,
bulk-memory-opt, multivalue, sign-ext, nontrapping-fptoint,
extended-const,
and call-indirect-overlong. Unlike the default "generic" CPU, "lime1" is
meant
to be frozen, and followed up by "lime2" and so on when new features are
desired.

[Lime1 CPU]:
https://github.com/WebAssembly/tool-conventions/blob/main/Lime.md#lime1

---------

Co-authored-by: Heejin Ahn <aheejin@gmail.com>

This defines some new target features. These are subsets of existing
features that reflect implementation concerns:

- "call-indirect-overlong" - implied by "reference-types"; just the
overlong encoding for the `call_indirect` immediate, and not the actual
reference types.

- "bulk-memory-opt" - implied by "bulk-memory": just `memory.copy` and
`memory.fill`, and not the other instructions in the bulk-memory
proposal.

This is split out from https://github.com/llvm/llvm-project/pull/112035.

---------

Co-authored-by: Heejin Ahn <aheejin@gmail.com>

We were prepared to enable these features [back in February], but they
got pulled for what appear to be unrelated reasons. So let's have
another try at enabling them!

Another motivation here is that it'd be convenient for the [Lime1
proposal] if "lime1" is close to a subset of "generic" (missing only
for extended-const).

[back in February]:
https://github.com/WebAssembly/tool-conventions/issues/158#issuecomment-1931119512
[Lime1 proposal]: https://github.com/llvm/llvm-project/pull/112035

This commit implements the [wide-arithmetic] proposal which has recently
reached phase 2 in the WebAssembly proposals process. The goal here is
to implement support in LLVM for emitting these instructions which are
gated behind a new feature flag by default. A new `wide-arithmetic`
feature flag is introduced which gates these four new instructions from
being emitted.

Emission of each instruction itself is relatively simple given LLVM's
preexisting lowering rules and infrastructure. The main gotcha is that
due to the multi-result nature of all of these instructions it needed
the lowerings to be implemented in C++ rather than in TableGen.

[wide-arithmetic]: https://github.com/WebAssembly/wide-arithmetic

This better aligns with how the feature is being referred to and what
runtimes (V8) are calling it.

This updates the list of features in 'generic' and 'bleeding-edge' CPUs
in the backend to match

https://github.com/llvm/llvm-project/blob/4e0a0eae58f7a6998866719f7eb970096a2a52e9/clang/lib/Basic/Targets/WebAssembly.cpp#L150-L178

This updates existing CodeGen tests in a way that, if a test has
separate RUN lines for a reference-types test and a non-reference-types
test, I added -mattr=-reference-types to the no-reftype test's RUN
command line. I didn't delete existing -mattr=+reference-types lines in
reftype tests because having it helps readability.

Also, when tests is not really about reference-types but they have to
updated because they happen to contain call_indirect lines because now
call_indirect will take __indirect_function_table as an argument, I just
added the table argument to the expected output.

`target-features-cpus.ll` has been updated reflecting the newly added
features.

This currently only defines a constant, but in the future will be used
to gate builtins for experimenting and prototyping half-precision
proposal (https://github.com/WebAssembly/half-precision).

Adding to allow users to get this flag into the target features section for
future use cases.

Reviewed By: tlively, aheejin

Differential Revision: https://reviews.llvm.org/D158409

Accompanying https://reviews.llvm.org/D125728, this updates LLVM
Codegen's "generic" CPU to enable the same new features.

Differential Revision: https://reviews.llvm.org/D125729