refactor(toast): Replace vue-toasted with BootstrapVue's Toast plugin

• Integration MR: gitlab!63919 (merged)

What does this MR do?

• Drops vue-toasted in favor of BootstrapVue's toast component.
• Use shared CloseButton component as toasts close button.

Screenshots

Context	Before	After
Default (toasts are now stackable)
With action
Long content

Migration notes

• The following options have been renamed:
  • duration now is autoHideDelay
  • className now is toasClass.
• The following options are not supported anymore:
  • fullWidth
  • fitToScreen
  • containerClass
  • iconPack
  • Icon
  • theme
  • closeOnSwipe
  • keepOnHover
  • singleton
  • type (note that while this option was previously supported, it didn't have any effect visually and can thus be removed altogether)
• It is not possible to render HTML in toasts' body anymore, make sure to only pass plain text to the .show() method.
• To adhere with the design system, the position option has also been removed. Toasts should only appear in the bottom-left corner.
• The callbacks have been backported:
  • onComplete should work as usual.
  • onClick's second argument is an object with the following properties:
    • id is the BootstrapVue toast's ID.
    • hide is a method that can be called to hide the toast. It replaces goAway(0).

Closes #246 (closed)

Closes #1125 (closed)