Add FLAG_ACTIVIY_REQUIRE_DEFAULT to test intents

This helps us notice when a test is failing because an implicit intent
is opening the ResolverActivity, which is never expected in our test
suites.

Test: atest SafetyCenterActivityTest
Bug: 287065919
Relnote: N/A
Change-Id: I2b03285633b7c01b981add583b2e4e441cdf8d4f