ColorPicker: improve UX of dragging the handle when in popover on top…

… of the editor (#55149)

* ColorPicker: expose drag start / end handlers via context

* ColorPicker: remove overflow hidden rule

* Dropdown: add some sort of backdrop to capture pointer events

* Add test story

* Prevent resizing on color palette's popover, which also triggers overflow: hidden

* Improve backdrop position by using react portal

* Cleanup

* Aria-hidden

* Cleanup

* Scope querySelector within color picker s container element

* Listen for drag events also on hue and alpha sliders

* Remove temporary styles

* Remove temporary storybook example

* CHANGELOG

* Move pointer events trap from Dropdown to Popover component

* Use state to grab ColorPicker's container element to make sure the component re-renders

* Remove overflow:hidden from PaletteEdit component's popover

* Update CHANGELOG

* Remove dead code

* Update snapshot

* Move newly added ColorPicker logic to a separate hook

* Add inline comment around the resize: false change

* Add more comments