[Spark] Add more Unity Catalog integration tests (delta-io#4626)

## Description
This extends coverage for Unity Catalog integration tests:
- Split tests across multiple suites
- Add coverage for DMLs using SQL, time-travel, streaming, ALTER TABLE,
utility functions, ...

## How was this patch tested?
Ran tests locally. These tests aren't executed automatically as part of
PR validation as they require provisioning external resources.

## Does this PR introduce _any_ user-facing changes?
No

Author: johanl-db