Refactor <TimePicker> to function component

[kevin940726]

Description

Refactor to function component following the latest best practices. Related to #22890. Notable changes are as follow.

• Refactored tests to use RTL, as per Drop and remove enzyme in favour of React Testing Utils or lightweight wrapper lib #17249.
• Add <TimePicker> story in storybook.
• Avoid syncing state and props as much as possible. Use an useEffect to reset the state when necessary.
• Truncate the date at the minutes at all time, related to Fix not truncating at minutes the first time in <TimePicker> #24305.

How has this been tested?

Several ways to test this:

1. Run the storybook and play with it in components/TimePicker.
2. Run the dev environment and play with it in the <PostSchedule> component when editing a post and scheduling post time.
3. Run the unit tests.

Types of changes

New feature

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.

[talldan]

This seems to be working really nicely, appreciate all the effort into changing the tests over to react testing library, and adding the story.

I spotted one bug with the month select, though as far as I can tell it also seems to happen in master, so it may be worth taking a look at in a separate PR.

A few separate code quality things, but nothing major 😄

[talldan]

Thanks for all the work on this!