Fixes cockroachdb#80655, mostly.

Previously, users had to type `1:03 PM (UTC)` in order to enter text into the time picker.

This commit modifies the time picker so that users would instead type either
- `1:03`, or
- `01:03`

to enter text into the time picker. Copying and re-pasting the text from a time picker still works.

Alternate approaches not pursued (these are not needed with the removal of AM/PM).

1) Make our own time picker component, and style it to look like antd's. There's
a general issue of antd's components not being keyboard friendly:
ant-design/ant-design#5685

2) Upgrade to `antd` version 4, and use an undocumented prop type. `antd`'s time
picker uses the time picker from the `rc-picker` library under the hood. In
`rc-picker`, the `format` prop is of type `String | String[]`, where if it's an
array the first value will be used for display and the remaining ones will be
used for parsing, as documented [here]
(https://react-component.github.io/picker). In theory, `antd` passes `format`
(and also any remaining, additional props in addition to the specified ones) to
the `rc-picker` component. So even though the `antd` `TimePicker` component
`format` prop is not documented to take in a string array, one might think that
passing in a string array anyway would work. In practice, passing in a string
array works in `antd` version `4.20.4`, as tested in the [antd sandbox]
(https://ant.design/docs/react/getting-started) (render `<TimePicker format={
["h:mm A", "h:mma"]}/>`). However, this does not work in our codebase
(which installs `antd` `v3.25.2`), or in the `antd` version `3.x` [sandbox]
(https://3x.ant.design/docs/react/getting-started). The errors that appear in
these two situations are different, and in a way demonstrate the potential for
breakage from using an undocumented feature in future upgrades from a version
that we've to work. If we do this, we should add a test.

3) Dead end: The `antd` `TimePicker` component takes an `onChange` prop with a
second `timeString` paramater. However, `onChange` only fires if the input is
of the correct, parsable format. The specific code that ignores text input that
is not of a parsable format is in `rc-picker`, [here]
(https://github.com/react-component/picker/blob/5306c8938aded49c5d6f6b6d4761ddab25e3cce9/src/Picker.tsx#L237).
This prevents us from being the one to do the fuzzy matching and passing the
value back to the component.

Release note (ui): The time picker component has been improved such that users
can use keyboard input to select a time without having to type `" (UTC)"`