fix(modal): reset footer positioning after content drag and multi-footer support (#30470)

Issue number: resolves #30468

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## What is the current behavior?
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Currently, if you use pointer events to drag the content of a sheet
modal with `expandToScroll` disabled and have you have a footer and a
dismiss button, then you use the dismiss button to close the modal, the
footer will be stuck in its pinned position at the bottom of the screen.

Additionally, if you have multiple footers, only one of them properly
gets pinned and unpinned.

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

- We now move footers back to their stationary position when we finish
our drag event on modal content
- We support pinning and unpinning multiple footers at the same time now

## Does this introduce a breaking change?

- [ ] Yes
- [X] No

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See
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## Other information

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

Dev build: `8.6.1-dev.11749575087.1b86eb67`