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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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.
597bc3f085