Move tests to SafetyCenterSubpagesTestCases

These are some of the slower tests, so seperate them from the rest to
increase changes of everything passing below runtime limits.

Bug: 292809502
Test: atest SafetyCenterFunctionalTestCases SafetyCenterSubpagesTestCases
Relnote: Split SafetyCenterSubpagesTestCases off of SafetyCenterFunctionalTestsCases in MTS
Change-Id: I6fea563b93a6edb1564f715f510702c0888f6b3f