[C++] Top-level `const` and `volatile` should not be present for function parameters

Describe the bug

void f(int), void f(int const), and void f(int volatile) are all the declarations for the same overload A C++ best-practice is to not const-qualify proper function declarations, and only function definitions. This is because one can declare f as void f(int const), and then define it as void f(int). You can verify this using this Compiler Explorer example.

Note that this doesn't apply to references. void f(int&) and void f(int const&) are different overloads, as demonstrated by this second Compiler Explorer example.

Top-level const-qualifier is redundant at best, but it's potentially misleading, since a reader may interpret this to mean that x won't change, which isn't guaranteed by a proper declaration, since the definition can change this up.

How to Reproduce

1. Create a default Sphinx project.
2. Add .. cpp:function:: int square(int const x, int volatile y); to index.rst.
3. Run make html.

Environment Information

Platform:              linux; (Linux-6.3.2-arch1-1-x86_64-with-glibc2.37)
Python version:        3.11.3 (main, Apr  5 2023, 15:52:25) [GCC 12.2.1 20230201])
Python implementation: CPython
Sphinx version:        6.2.1
Docutils version:      0.18.1
Jinja2 version:        3.1.2
Pygments version:      2.15.1

Sphinx extensions

No response

Additional context

No response

Reproduce the issue in a default Sphinx project by adding the cpp:function directive to index.rst and running make html. Trace how the C++ signature is parsed and rendered, using the examples in the report to distinguish top-level qualifiers from reference qualifiers; done means the generated documentation omits redundant top-level const and volatile qualifiers without changing reference overloads.