Add tests for a desktop app opening using KB shortcut

Adds a new flicker and functuinal tests and a scenario to open a desktop
mode app using the 'Action + B' keyboard shortcut.

Test: atest OpenBrowserWithKeyboardShortcutFlickerTest
Bug: 418232742
Flag: EXEMPT, not needed for e2e tests
Change-Id: Ibc8b977383bc1948a5bfe32690da39149224d32a