[Improvement] Misleading `IT` suffix in test class

### What would you like to be improved?

Some test class has the `IT` suffix, e.g. `XXXTableOperationsIT`, `TestMysqlDatabaseOperations`, `TestPostgreSqlSchemaOperations`. But integration test means end-to-end testing.
Should we remove the misleading suffix?

### How should we improve?

Maybe we can revisit all the test classes in test folder to see which of them are end to end testing and remove the suffix from all other classes.

Start by inventorying the test folder, including XXXTableOperationsIT, TestMysqlDatabaseOperations, and TestPostgreSqlSchemaOperations, and determine which classes are end-to-end tests. Define the naming rule before making changes; done means non-end-to-end classes no longer carry the misleading IT suffix and the renamed tests remain runnable.

Written by the indexing model from the issue text.