Changes

feat(pingcap/tidb): add new integration test job for BR next-gen (#3592)

- Introduced a new Jenkins pipeline job for the
`pull_br_integration_test_next_gen`, including its configuration in the
job DSL and Prow presubmits.
- Created associated pipeline and pod specifications to facilitate the
integration testing process.
- Implemented caching and resource management for Kubernetes pods to
optimize performance.

This addition enhances the CI/CD capabilities for the TiDB project,
ensuring robust testing for the BR integration.

Close #3581

Signed-off-by: wuhuizuo <wuhuizuo@126.com>
 (commit: b91d588)