Integrates tests for TTL behavior

[killme2008]

What type of enhancement is this?

Tech debt reduction, Other

What does the enhancement do?

GreptimeDB misses integration tests for TTL behavior. The developer only tests it manually or creates some simple cases in unit tests.

We need to add black box tests for it, especially for both of the table engines: the mito engine and the metric engine.

Implementation challenges

Written in sqlness, but needs to trigger the expiration forcibly.