Handle permission grant for TextClassifierService.

The trust TextClassifierServices are defined in config.xml, and the first
one package is the default system TextClassifier service. Grant permissions
to default TextClassifier Service.

Bug: 141111813
Bug: 146391636
Test: Manual. Use dumpsys pm to check package runtime permissions.
Test: atest GtsPermissionTestCases:com.google.android.permission.gts.\
DefaultPermissionGrantPolicyTest#testDefaultGrantsWithRemoteExceptions

Change-Id: Iff2dec1e44515d97cc38bb336d19d5df29f1c097