Use enableSplitContextually() to guard split keyboard shortcut feature

enableSplitFromFullscreenWithKeyboardShortcuts() depends on enableSplitContextually() from the product perspective, hence merging these two flags

Bug: 270394122
Test: N/A
Change-Id: Iecf46a62bfa21ed0c3bad9ca8c9e2646b3aebc78
3 files changed