* Remove a mixin - mx_Tooltip_dark
The mixin has been used on `_AppsDrawer.pcss` only.
* Rename mx_Tooltip_dark based on the naming policy
'mx_Tooltip_dark' has been used on `AppPermission.tsx` only.
* Nesting: `mx_ResizeHandle`
* Nesting: `> div`
* Run prettier
* Use a custom property
* Remove a redundant declaration: `cursor: row-resize`
The resizer is either vertical or horizontal, and since `cursor: row-resize` is applied by default, it does not need to be repeated here.
* Conform the class names to the naming policy
* Revert "Use a custom property"
This reverts commit 6116939eec7d9e4220b89a638623e5876e143adf.
* Replace a Sass variable with a CSS custom property - $container-gap-width
* Replace a Sass variable with a CSS custom property - $container-border-width
* Remove unnecessary PipContainer component
* Redesign the picture-in-picture window
* Add a hover effect to the controls
* Clarify that WidgetPip has call-specific behavior
