Add ComponentCaller APIs for Activity's new intents

With activities potentially receiving multiple intents at the same time,
it is important to match intents to their callers correctly. Hence, this
change overloads existing onNewIntent with a ComponentCaller -
onNewIntent(Intent, ComponentCaller).

To supplement the new overload, this CL adds these Activity APIs:
- getCurrentCaller() - only works within onNewIntent(), should be used
  by those that don't override the new overload of onNewIntent.

- setIntent(Intent, ComponentCaller) - to keep the new intent caller for
  future use.

- getCaller() - to retrieve the caller associated with the intent from
  getIntent().

Finally, this change adds an Instrumentation API:
callActivityOnNewIntent(Activity, Intent, ComponentCaller).

Bug: 293467489
Test: atest CtsAndroidAppTestCases:android.app.cts.ShareIdentityTest
Test: atest CtsAndroidAppTestCases:android.app.cts.ComponentCallerTest
Test: atest CtsAppTestCases:android.app.cts.InstrumentationTest
Change-Id: I6e2457171e910fa3d05430f62db8d735ce324f5a