Added table metric & Improved the database / view metric & Added "count databases" for table model

[Caideyipi]

Description

As the title said.

ConfigNode:

DataNode:

---

This PR has:

• [x] been self-reviewed.
  • [ ] concurrent read
  • [ ] concurrent write
  • [ ] concurrent read and write
• [ ] added documentation for new or modified features or behaviors.
• [ ] added Javadocs for most classes and all non-trivial methods.
• [ ] added or updated version, license, or notice information
• [ ] added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• [ ] added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage.
• [ ] added integration tests.
• [x] been tested in a test IoTDB cluster.

---

Key changed/added classes (or packages if there are too many classes) in this PR