Closes #4644

Release Notes:

- Adds `MousePressureEvent`, an event that is sent anytime the touchpad
pressure changes, into `gpui`. MacOS only.
- Triggers go-to-defintion on force clicks in the editor.

This is my first contribution, let me know if I've missed something
here.

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Co-authored-by: Anthony Eid <anthony@zed.dev>
Co-authored-by: Antonio Scandurra <me@as-cii.com>