feat(dsl): add MongoDB connector

[johntomcat7408-cmyk]

What changes were proposed in this pull request?

• Add a MongoDB source and sink connector with SPI registration.
• Support bounded reads, explicit integer range partitions with [lowerbound, upperbound)
  boundaries, and count offsets.
• Support ordered batch inserts and BSON type conversion.
• Add connector configuration, unit and integration tests, GQL example, and CN/EN docs.

The source targets static collections. CDC, upsert, automatic retry, and exactly-once delivery
are not included.

Closes #797.

How was this PR tested?

• Tests have been added for the changes

• Production environment verified

• MongoTableConnectorTest and MongoRowConverterTest: 12 tests passed.

• MongoTableConnectorIT: passed with Docker in
  GitHub Actions;
  0 failures, errors, or skips.

• Maven verify, Checkstyle, Apache RAT, and dependency tree checks passed.

[johntomcat7408-cmyk]

I verified PR merge commit b42bc097a2b144e0ae9713bb44af174d1cfb5983 (head 148d4791bf2f8199b0703077b26ecba7940d2713) locally on Windows 11 with Oracle JDK 8u451, Maven 3.8.9, and protoc 3.21.7.

• All 107 modules compiled successfully, including test sources (mvn ... -DskipTests).
• MongoDB connector unit tests passed: 12 tests, 0 failures.

The failed JDK 8 job stopped at setup-protoc due to GitHub API rate limiting before Maven started. Could you please rerun it?