[feat][io] Add Debezium CockroachDB source connector

## Motivation

Debezium ships a CockroachDB source connector (`io.debezium:debezium-connector-cockroachdb`, present in the `debezium-bom` at our pinned version), but this repository does not wrap it. We currently wrap 5 of Debezium's 12 source connectors: MySQL, PostgreSQL, MongoDB, Oracle, and SQL Server.

Unlike the other gaps, this connector does **not** use the logical-decoding or binlog machinery — it consumes CockroachDB's native **changefeeds**.

## Proposal

Add a `debezium/cockroachdb` module (`pulsar-io-debezium-cockroachdb`) following the structure of the existing Debezium modules:

- `DebeziumCockroachDbSource` extending `DebeziumSource`
- `include("debezium:pulsar-io-debezium-cockroachdb")` in `settings.gradle.kts`
- `debezium-connector-cockroachdb = { module = "io.debezium:debezium-connector-cockroachdb" }` in the version catalog
- NAR packaging + distribution wiring
- A Testcontainers integration test using the `cockroachdb/cockroach` image (`start-single-node --insecure`), enabling rangefeeds (`SET CLUSTER SETTING kv.rangefeed.enabled = true`) and creating a changefeed in setup

## Notes

- **This is the newest and least battle-tested connector of the set** — it arrived in the 3.4 line. Treat it as lower priority than #65 (MariaDB) and Db2 unless there is concrete user demand, and expect the connector's own behavior to shift across Debezium minors (see the migration tracked in #63).
- Because it uses native changefeeds rather than the standard relational CDC path, verify the emitted record shape and offset semantics match what `DebeziumSource` and `PulsarSchemaHistory` expect — it may not need schema history at all.
- Use the `GenericContainer` pattern (see the Testcontainers version conflict noted in #62).

_Identified by a scan of the Debezium connector catalog against our connector inventory._

Start by comparing the existing Debezium modules and their NAR and distribution wiring, then inspect settings.gradle.kts and the version catalog. Build the module around DebeziumCockroachDbSource and use a GenericContainer integration test with the cockroachdb/cockroach image, rangefeeds, and a changefeed. Done means the module is packaged and wired into the distribution, and the test verifies emitted records and offset semantics.

Written by the indexing model from the issue text.