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`.

As part of the Root Signature Spec, we need to validate if Root
Signatures are not defining overlapping ranges.
Closes: https://github.com/llvm/llvm-project/issues/126645

---------

Co-authored-by: joaosaffran <joao.saffran@microsoft.com>
Co-authored-by: Joao Saffran <{ID}+{username}@users.noreply.github.com>
Co-authored-by: Joao Saffran <jderezende@microsoft.com>

When implementing #146785, notice `DXILRootSignature` had some design
changes that made it harder to integrate with other analysis. This
change refactors `DXILRootSignature` to solve this issue.
---------

Co-authored-by: joaosaffran <joao.saffran@microsoft.com>

The DXILResourceMap stores more information about resource instances
than just their binding.

Fixes https://github.com/llvm/llvm-project/issues/134741

Moves Resource Instance properties from type info into resource info as
described in
https://github.com/llvm/wg-hlsl/blob/main/proposals/0022-resource-instance-analysis.md

- Remove calls to pass initialization from pass constructors.
- https://github.com/llvm/llvm-project/issues/111767

Non-functional change as first step in
https://github.com/llvm/wg-hlsl/pull/207

Removes `Binding` from "Resource Instance" types

DXC and the DXIL validator expect resources in a DX container to be
specifically ordered CBuffers, Samplers, SRVs, and then UAVs. Match this
behaviour so that we can pass the validator.

Fixes #130232.

Adding support for Root Signature Flags Element extraction and writing
to DXContainer.
- Adding an analysis to deal with RootSignature metadata definition
- Adding validation for Flag
- writing RootSignature blob into DXIL

Closes: [126632](https://github.com/llvm/llvm-project/issues/126632)

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Co-authored-by: joaosaffran <joao.saffran@microsoft.com>