Allow custom spinners across rich library

[MaddyGuthridge]

Type of changes

• New feature
• Documentation / docstrings
• Tests

Checklist

• I've run the latest black with default args on new code.
• I've updated CHANGELOG.md and CONTRIBUTORS.md where appropriate.
• I've added tests for new code.
• I accept that @willmcgugan may be pedantic in the code review. (I am keen!)

Description

Resolves #3790

The feature

• Adds type definition to spinner animation dictionary
• Allows a custom spinner animation parameter in place of a spinner name, allowing users to specify their very own animations if they desire
• This is implemented in Spinner, Console.status, Status and progress.SpinnerColumn (let me know if I missed anything)

Documentation

• I documented custom spinner support in console.rst
• Spinners don't have their own dedicated documentation page. Should one be added? If so, this should be documented there.
• Notably, all tests still pass.

Is this worth adding despite Rich rejecting most new features?

• Imo this feature is worthwhile adding, since it cannot easily be added through a third-party library (unless that library reimplements spinners as a whole). Imo this makes it easier to extend the core library.
• This shouldn't break backwards compatibility, as all changed function parameters still accept their original types, as well as the new types.

Design considerations

• In an ideal world, all these functions would accept a Spinner object themselves, rather than their assorted set of other parameters (spinner, spinner_style and speed), which would make patterns like dependency injection simpler
• However, accepting a Spinner object (rather than constructing one based on these parameters) would make those other parameters ambiguous in the case where a Spinner object is given.
• As such, this design is probably the best for fitting with the existing code-base, and avoiding confusion and breaking changes.

[MaddyGuthridge]

Hello, @willmcgugan. I'd appreciate a review of this if possible. I'd love to have custom spinners for my CLI apps that use Rich, and have gotten a comment on the linked issue saying that I'm not the only one who would like this.