Convert more type annotations to latest Python built-in

[mhucka]

Recent versions of Python offer updated type annotation syntaxes. Cirq should make use of them.

[pavoljuhas]

Per PEP-585 we should use list[int] instead of typing.List[int] for type annotations. The ruff tool has an option to automate the fixup of old-style annotations - https://docs.astral.sh/ruff/rules/non-pep585-annotation/

We can also replace Union[str, int] with str | int and Optional[int] with int | None.
This can be checked with pylint rule consider-alternative-union-syntax

cc @codrut3

[Akshita07]

Is anyone working on this? And is there already a related PR? If no one has already claimed it, I want to work on this task.

[codrut3]

Feel free to do this @Akshita07 Otherwise I'll have a look in a couple of days.

[Akshita07]

Thank you @codrut3 :)

[mhucka]

@Akshita07 OK, I've assigned it to you. Thank you for your interest!

With respect to this question: "is there already a related PR": there was not for this specific matter, but there is an ongoing series of PRs from @pavoljuhas to make some other type annotation updates. I don't think the changes will interfere with each other, but you may still want to take a look in the closed PRs for recent type annotation-related PRs by Pavol, and just look at what the changes involved.

[pavoljuhas]

Thanks @Akshita07 for your offer to help! I have an ongoing series of PRs to address #1999 which should be wrapped up by mid next week. It is probably better to hold on with your changes so there is no interference; that said, any files that were already touched in #7193, #7278, #7295, #7298, #7317, #7325, #7343 are safe to work on.

[Akshita07]

Thanks @mhucka and @pavoljuhas for the information. I'll check the closed PRs and make my changes accordingly.