Migrate SearchViewUiTest to JUnit 4 for upcoming test addition

An upcoming change requires JUnit 4 to be used to filter tests, migrate
the underlying class as a precursor to this change to avoid having the
change contain unnecessary updates.

Bug: 405288522
Test: atest com.android.documentsui.SearchViewUiTest
Flag: com.android.documentsui.flags.use_material3
Change-Id: Ibadfaae7fb933cf3a8cdf97467e0ae035968f5c7