Add unit test for ImeSubtypeListItem equals and hashCode

Adds a new test method, `testEqualsAndHashCode`, to verify the correctness of the `equals` and `hashCode` implementations in the `ImeSubtypeListItem` class.

The test covers the following scenarios:
- Equality with self, null, and different object types.
- Equality and hash code consistency for two equivalent items.
- Inequality for items where each of the fields is different, ensuring all fields are checked.

Please help fill out the survey for feedback: https://docs.google.com/forms/d/e/1FAIpQLSeKFKpHImCAqZIa_OR801cw72HQUreM2oGM25C3mKKT2tBFnw/viewform?usp=pp_url&entry.1586624956=ag/35402599

Please feel free to use your domain knowledge to make changes to the generated tests to make it more valuable for your team.
Original Change: ag/34763598
Test: ATP tests passed http://go/forrest-run/L87400030017394713
Bug: 431235865
Flag: TEST_ONLY

Change-Id: Ib5ac1da458196338e8bd1d0a9f9e2d11bc72b1c5