Add Redis adapter tests

[BobbieBarker]

• Fix RedisCase to properly set persistent_term adapter and resolve capabilities (was only setting Application env which SchemaCache doesn't read first)
• Fix RedisAdapter mget/1 to handle empty key list (Redis rejects bare MGET)

[codecov]

The changes in the diff encompass additions of new test cases, addition of new Redis operations in the adapter, and updates to the Redis test setup. The changes are by-and-large correct, however, there are areas for potential improvement. The main issues lay with hard-coded values in tests, lack of error handling, non-standard return values, and missing key features in the Redis adapter. These issues are detailed in the comments below.

[codecov]

Overall, the implementation is solid and adheres to the best practices in using redis and ETS. But, there are still a few improvements needed, most of them centered around error handling and the proper use of persistent_term.