TimeInput: Add label prop

[mirka]

Part of #52734
Follow-up to #60613

What?

Adds a label prop to TimeInput.

Why?

Since some people will be using this as an alternative to TimePicker, we need a way to add a visual label as well. (Technically, it needs to be a fieldset legend rather than a label.)

Testing Instructions

See Storybook for TimeInput to test behavior.

(Code changes are easier to review with whitespace hidden)

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[tyxla]

Tested with and without a label - works as expected, thanks! 🚀

[ciampo]

Should we consider making the label required by default, so that when the input is used standalone consumers are nudged towards labelling it? We could disable the rule when compositing is in DateTimePicker.

[mirka]

I don't think it's a huge issue for this one specifically, because the hours and minutes inputs are both labeled.

In the general case though (re: #51740), I'm starting to think that an eslint rule for our repo might be a good way to nudge devs without compromising the "truthfulness" of our TS types.