[Unchecked] Fix unchecked warnings in chrome/android & webview tests

Fix approaches:
 - Diamond operators and fully parameterized locals replacing raw
   Pair/AtomicReference/PayloadCallbackHelper/ListModelChangeProcessor
   constructors.
 - Class-level @Mock / @Captor fields replacing raw mock(Class.class)
   and ArgumentCaptor.forClass() locals. Existing @Captor fields
   reused in place of any(Class.class) matchers where available.
 - @SafeVarargs wrappers (safeReset, safeClearInvocations, asSet,
   arrayToSet) replacing method-level @SuppressWarnings on generic-
   varargs Mockito/helper calls.
 - Class<T>.cast(obj) replacing raw (T) obj casts where a Class
   token is in scope (BookmarkTest, DisplayCutoutTestRule).
 - Covariant return overrides in RegularTabSwitcherStation and
   IncognitoTabSwitcherStation delegating to super.openAppMenu() to
   parameterize transit facility return types without code
   duplication; TabSwitcherGroupCardFacility.openAppMenu() narrowed
   to TabSwitcherStation host type.
 - Unwrap Hamcrest allOf(singleMatcher).
 - Narrow method-scope @SuppressWarnings("unchecked") with justifying
   comment only for unavoidable sites

This is part of the effort to enable -Xlint:unchecked globally.

Bug: 358366667
Change-Id: I540a67192e4421d46e056ac60edb28b3ad0d7cb9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7790135
Owners-Override: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1619472}