Add android:usesNonSdkApi manifest attribute

ActivityManagerService decides on the non-SDK API enforcement policy
of every newly spawned process. System apps can be exempted by adding
their package name to a config XML file, tests can pass a flag to
'am instrument'. This patch adds a new @hide attribute on the <application>
manifest tag, "android:usesNonSdkApi", which can be used by both
system apps and tests, and is automatically set by the build system.

The use of the attribute remains guarded as follows:
- if invoked via 'am instrument', must hold shell user permission,
- if app launched, must be a system app or an updated system app.
The attribute is ignored in all other cases.

Bug: 113315999
Test: N/A
Change-Id: I2f6cb56f63fa2c5dd6c7c25fcefe8205da1ec96a