feat(datetime): add support for h11 and h24 hour formats (#28219)

Issue number: resolves #23750

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## What is the current behavior?
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Datetime does not support h11 and h24 hour formats

## What is the new behavior?
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this PR. -->

- Datetime supports h11 and h24 formats

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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and migration path for existing applications below. -->


## Other information

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screenshots of how the component looks before and after the change. -->


Implementation Notes:

1. I broke up the `is24Hour` function into two functions:
- The first function, `is24Hour`, accepts an hour cycle and returns true
if the hourCycle preference uses a 24 hour format
- The second function, getHourCycle, accepts a locale and an optional
hour cycle and returns the computed hour cycle. I found that the hour
cycle is not always set via `hourCycle` (such as when we are using the
system default if it's specified in the `locale` prop using locale
extension tags). This was coupled to is24Hour, but I needed this
functionality elsewhere to add support for this feature, so I decided to
break the functions up.
2. We were using the hour cycle types in several places, so I decided to
create a shared `DatetimeHourCycle` to avoid accidental typos.

core/src/components/datetime/datetime-interface.ts

@@ -34,3 +34,5 @@ export type DatetimeHighlightStyle =
 export type DatetimeHighlight = { date: string } & DatetimeHighlightStyle;
 
 export type DatetimeHighlightCallback = (dateIsoString: string) => DatetimeHighlightStyle | undefined;
+
+export type DatetimeHourCycle = 'h11' | 'h12' | 'h23' | 'h24';