Remove custom schema parsing in favor of Uri

This allows TextClassifier models to add support for additional protocols
after launch.

Bug: 79407639
Test: atest FrameworksCoreTests:TextClassificationManagerTest
Test: atest FrameworksCoreTests:TextClassificationTest
Test: atest CtsViewTestCases:TextClassificationManagerTest
Test: atest CtsViewTestCases:TextClassifierValueObjectsTest
Change-Id: I6781bf476f8c81d2106e2fb73b8f4629068bb0af