## Summary
Part of https://github.com/astral-sh/ruff/issues/15382
This PR implements a general callable type that wraps around a
`Signature` and it uses that new type to represent `typing.Callable`.
It also implements `Display` support for `Callable`. The format is as:
```
([<arg name>][: <arg type>][ = <default type>], ...) -> <return type>
```
The `/` and `*` separators are added at the correct boundary for
positional-only and keyword-only parameters. Now, as `typing.Callable`
only has positional-only parameters, the rendered signature would be:
```py
Callable[[int, str], None]
# (int, str, /) -> None
```
The `/` separator represents that all the arguments are positional-only.
The relationship methods that check assignability, subtype relationship,
etc. are not yet implemented and will be done so as a follow-up.
## Test Plan
Add test cases for display support for `Signature` and various mdtest
for `typing.Callable`.
## Summary
This is related to #13778, more specifically
https://github.com/astral-sh/ruff/issues/13778#issuecomment-2513556004.
This PR adds various test cases where a keyword is being where an
identifier is expected. The tests are to make sure that red knot doesn't
panic, raises the syntax error and the identifier is added to the symbol
table. The final part allows editor related features like renaming the
symbol.
