Switch to the `.Cases({S0, S1, ...}, Value)` overload instead, and the
manually-enumerated overloads with 6+ arguments are getting deprecated
in https://github.com/llvm/llvm-project/pull/163405.

This pre-commits API updates ahead of the deprecation to make potential
reverts cleaner. This was already reviewed in #163405.

Add toolchain support for the
[WALI](https://doc.rust-lang.org/rustc/platform-support/wasm32-wali-linux.html)
target as per its corresponding
[RFC](https://discourse.llvm.org/t/rfc-new-wasm-linux-target-support/88203)

Summary:
This patch has broken the `libc` build bot. I could work around that but
the changes seem unnecessary.

This reverts commit 9ba844eb3a21d461c3adc7add7691a076c6992fc.

When handling CUDA ELF files via objdump or LLDB, the ELF parser in LLVM
needs to distinguish if an ELF file is sass or not, which requires a
triple for sass to exist in llvm. This patch includes all the necessary
changes for LLDB and objdump to correctly identify these files with the
correct triple.

This pr implements support for a root signature as a target, as specified
[here](https://github.com/llvm/wg-hlsl/blob/main/proposals/0029-root-signature-driver-options.md#target-root-signature-version).

This is implemented in the following steps:
1. Add `rootsignature` as a shader model environment type and define
`rootsig` as a `target_profile`. Only valid as versions 1.0 and 1.1
2. Updates `HLSLFrontendAction` to invoke a special handling of
constructing the `ASTContext` if we are considering an `hlsl` file and
with a `rootsignature` target
3. Defines the special handling to minimally instantiate the `Parser`
and `Sema` to insert the `RootSignatureDecl`
4. Updates `CGHLSLRuntime` to emit the constructed root signature decl
as part of `dx.rootsignatures` with a `null` entry function
5. Updates `DXILRootSignature` to handle emitting a root signature
without an entry function
6. Updates `ToolChains/HLSL` to invoke `only-section=RTS0` to strip any
other generated information

Resolves: https://github.com/llvm/llvm-project/issues/150286.

##### Implementation Considerations
Ideally we could invoke this as part of `clang-dxc` without the need of
a source file. However, the initialization of the `Parser` and `Lexer`
becomes quite complicated to handle this.

Technically, we could avoid generating any of the extra information that
is removed in step 6. However, it seems better to re-use the logic in
`llvm-objcopy` without any need for additional custom logic in
`DXILRootSignature`.

fixes #156068

- We needed to add a new sub arch to the target tripple so we can test
that emulation does not happen when targeting SM6.9
- The HLSL toolchain needed to be updated to handle the conversion of
strings to enums for the new sub arch.
- The emulation is done in DXILIntrinsicExpansion.cpp and needs to be
able to convert both llvm.is.fpclass and lvm.dx.isinf to the proper
emulation
- test updates in TargetParser/TripleTest.cpp, isinf.ll, is_fpclass.ll,
and DXCModeTest.cpp

For context, CheriotRTOS is a custom RTOS co-designed for the CHERIoT
CHERI-enabled RISCV32E platform. It uses a custom ABI and linkage model,
necesitating representing it in the target triple.

Ref:
https://ai.meta.com/blog/next-generation-meta-training-inference-accelerator-AI-MTIA/
This PR contains 
1. MTIA: Meta Training and Inference Accelerator as Environment.
2. Meta as the vendor.


### Testing 
Added a unittest for the relevant changes

### Reviewers
@clayborg , @jeffreytan81 , @Jlalond

These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

Add support for big-endian RISC-V ELF files:
  - Add riscv32be/riscv64be target architectures to Triple
- Support elf32-bigriscv and elf64-bigriscv output targets in
llvm-objcopy
- Update ELFObjectFile to handle BE RISC-V format strings and
architecture detection
  - Add BE RISC-V support to RelocationResolver
  - Add tests for new functionality

This is a subset of a bigger RISC-V big-endian support patch, containing
only the llvm-objcopy and libObject changes. Other changes will be added
later.