[CD Testing] Add test rule to setup connected display(s)

With this test rule, tests could run
```
@Rule @JvmField
val displayRule = SimulatedConnectedDisplayTestRule()

displayRule.setupTestDisplays(2)
```

This will allow connected displays test to be added for scenario and
flicker tests

Bug: 380001108
Test: presubmit
Flag: EXEMPT adding new tests
Change-Id: Ia7cc5b41b9915395ef6fd3bbe71112f33a2eaf49