perf(sheet): fixing performance regression on modal sheets when expandToScroll is false (#30267)

Issue number: internal

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## What is the current behavior?

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Currently, when a sheet is moved while `expandToScroll` is disabled, the
DOM is queried excessively causing performance degradation.


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

We now cache the targeted element in `onStart` and refer to it in
`onMove` and `onEnd`, preventing over-querying the DOM

## Does this introduce a breaking change?

- [ ] Yes
- [X] No

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## Other information

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screenshots of how the component looks before and after the change. -->
This regression was introduced in #30257 and quickly highlighted by a
member of the community