Add a flag byForegroundService to enqueueNotification() call.

This flag is passed to NotificationManagerService, the CallStyle check
will treat byForegroundService flag same as isFgs flag.

Only the ServiceRecord.postNotification() call at startForeground() call has
byForegroundService flag set to true.

Add a test case NotificationManagerServiceTest.java#checkCallStyleNotification_allowedForByForegroundService

Bug: 280003654
Test: atest NotificationManagerServiceTest.java#checkCallStyleNotification_allowedForByForegroundService
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:ea56bb0813c03d4b9d14795da979da8c86b8ccb1)
Merged-In: Ibe30526ac0ff52e2e4fe9bc846576509cdf78236
Change-Id: Ibe30526ac0ff52e2e4fe9bc846576509cdf78236