Expose more types for better static typing options

[tlauli]

Hi, I have two small improvements to static typing. This is my first contribution, so hopefully I did it right.

Contributor Checklist

• I have broken down my PR scope into the following TODO tasks
  • Introduce ComponentSingleType, representing a singular renderable entity -> it is possible to render a list of these
  • Make _Wildcard type public by renaming it to Wildcard, and making it an Enum, which I feel better reflects the intent behind it, plays nice with static type-checkers and prevents users from doing funky stuff with it since it is now public (subclassing or instantiating anything other than the tree variants defined by dash)
• I have run the tests locally and they passed. (refer to testing section in contributing)
• I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR.

optionals

• I have added entry in the CHANGELOG.md
• If this PR needs a follow-up in dash docs, community thread, I have mentioned the relevant URLS as follows
  • this GitHub #PR number updates the dash docs
  • here is the show and tell thread in Plotly Dash community

[T4rk1n]

This type is also duplicated on generate components for backward compatibility. The template is here:

dash/dash/development/_py_components_generation.py

Lines 28 to 35 in 1163158

	ComponentType = typing.Union[
	str,
	int,
	float,
	Component,
	None,
	typing.Sequence[typing.Union[str, int, float, Component, None]],
	]

[tlauli]

I replaced the duplicated code with import from the base_component, is that ok?

[T4rk1n]

No, it's for backward compatibility of generated components in external components libraries, if the library is built with the new imports but used with a previous version of dash it would not work.

[tlauli]

Oh, I see. I removed the import and used the new type.

[tlauli]

Would it be ok to replace the duplicated code with the import for 4.0?

[T4rk1n]

No, it's really just building the components need to be backward compatible as we don't want to force components libraries to depend on a particular version of dash.

[T4rk1n]

💃