Add TEST_MAPPINGs for toasts

Following revert of ag/9699132 due to related broken tests that weren't
executed in presubmit.

Test: croot frameworks/base/core/java/android/app && atest --dry-run --test-mapping
Test: croot frameworks/base/core/java/android/widget && atest --dry-run --test-mapping
Test: croot frameworks/base/services/core/java/com/android/server && atest --dry-run --test-mapping
Change-Id: I819cf354315e240b28dba294c08cf08bba6aada2