[Chromecast] Modernize org.chromium.chromecast.base.

This includes several refactors:

  * Use java.util.function functional interfaces instead of
    equivalents defined in org.chromium.base or
    org.chromium.chromecast.base.
  * Use default and static methods in Scope and Observer
    instead of separate Scopes and Observers helper classes.
  * Scopes.combine() is replaced with Scope.and().
  * Rename onEnter and onExit to onOpen and onClose to be more
    consistent with terminology in Observer and Observable
    interfaces.
  * Remove unused Itertools class.

Bug: 1034012
Bug: b/265858720
Test: cast_base_junit_tests
Test: cast_shell_junit_tests
Change-Id: Id5567ca04a88ca95d6331af1311721c8cc94bcde
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4175903
Auto-Submit: Simeon Anfinrud <sanfin@chromium.org>
Commit-Queue: Yuchen Liu <yucliu@chromium.org>
Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1101303}