Bump UI automator timeout to 15s.

Some tests seem to flakily fail under the 10s mark.
Bumping this to 15s should hopefully still give us about 3 tries if
the RetryRule is used.

Also add the RetryRule to SafetyCenterActivityTest as they seem to flake.

Bug: 240424992
Test: atest SafetyCenterFunctionalTestCases
Relnote: N/A
Change-Id: I0ce302b2086b895aac7b5f0096ddd1bfd33017d1