Mark BindServiceFlags.getValue() @hide.

Change BIND_EXTERNAL_SERVICE_LONG to 1L << 62 (from 1L << 63), do not
use the sign bit.

Bug: 271325720
Test: atest cts/tests/app/src/android/app/cts/ServiceTest.java#testBindServiceFlags
atest cts/tests/app/src/android/app/cts/ServiceTest.java
atest cts/tests/app/src/android/app/cts/ActivityManagerProcessStateTest.java
atest cts/tests/app/src/android/app/cts/ActivityManagerFgsBgStartTest.java

Change-Id: I8fb9be68493c9f4b631c0e33ad3089b03245770c