Fix flaky test

Attempts to fix a flaky test by ensuring that recents is always cleared before creating a split pair (so the split pair under test is always the same).

Bug: 340935208
Test: testSaveAppPairMenuItemOrActionExistsOnSplitPair(), testSplitTaskTapBothIconMenus()
Flag: TEST_ONLY
Change-Id: Ibc81b90fac531f0e78e93a494ff59073ab5e52cf
5 files changed