feat(range): add label prop (#27408)

Issue number: N/A

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## What is the current behavior?
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Labels on `ion-range` can only be set via the `label` slot. When only
plain text is needed, this is cumbersome because you need to add an
entire new element to wrap the label.

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

Label prop added. If both the prop and slot are used, the prop will take
priority.

## 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. -->

- Docs PR: https://github.com/ionic-team/ionic-docs/pull/2955
- Dev build: `7.0.6-dev.11683657201.139d03f4`