[python] Move kernel signature inference out of MLIR compilation

[lmondada]

I've broken up this PR into two commits that can be reviewed independently:

The first commit contains "clean-ups". It doesn't introduce any new functionality nor should it change how anything is currently working. It just removes function arguments that aren't used, renames a couple of things and should make the code more readable. I'm including this here because it made my actual work much easier. These breaking changes are acceptable as they are within the python/cudaq/kernel folder, which is not publicly exposed (discussed with Bettina).

The second commit is the real contribution:

• The main goal is to parse the kernel signature before running the MLIR compilation. This is required so that we can delay MLIR compilation until the first kernel invocation (in a future PR).
• To this end, an AST visitor in python/cudaq/kernel/analysis.py is extended to parse the function annotations. This can be run before MLIR compilation
• A type KernelSignature is introduced to consolidate all kernel type information that was scattered across many attributes in one place.
• KernelSignature now only stores the kernel types as MLIR types (before, both Python and MLIR types were stored). This makes it easier to handle as there is a single source of truth (and Python types can be recovered using mlirTypeToPyType)

EDIT: Added a third commit that fixes issue #2895

I've noted that a lot of this Python code uses CamelCase, even though our style guide (Google style guide) recommends snake_case. I'm using snake_case where new names/variables are introduced, but limited the number of existing names that had to be changed.

closes #2895

[lmondada]

EDIT: done

Note: I've already rebased on top of #3932 but am waiting for that to get merged in. In the meantime ignore commit cec7875 as it has already been reviewed. Will do a final rebase on main when that's possible.

[github-actions]

CUDA Quantum Docs Bot: A preview of the documentation can be found here.

[khalatepradnya]

Commit#1 looks good. One Q.

[khalatepradnya]

Commit#2 looks good to me.
One minor comment and request to extend tests.

[khalatepradnya]

Suggest moving commit# 3 in a separate PR.

[taalexander]

At a high-level this looks good to me. As I am unfamiliar I will leave to others to approve.

[github-actions]

CUDA Quantum Docs Bot: A preview of the documentation can be found here.

[github-actions]

CUDA Quantum Docs Bot: A preview of the documentation can be found here.

[github-actions]

CUDA Quantum Docs Bot: A preview of the documentation can be found here.

[khalatepradnya]

LGTM. Thanks, @lmondada !

[github-actions]

CUDA Quantum Docs Bot: A preview of the documentation can be found here.