* Pulled `FinderBase` out of `Finder`
  * `FinderBase` can be used for any object, not just elements
  * Terminology was updated to be more "find" related
* Re-implemented `Finder` using `FinderBase<Element>`
  * Backwards compatibility maintained with `_LegacyFinderMixin`
* Introduced base classes for SemanticsNode finders
* Introduced basic SemanticsNode finders through `find.semantics`
* Updated some relevant matchers to make use of the more generic `FinderBase`

Closes #123634
Closes #115874