Changes

opt(prow-jobs/pingcap/ticdc): refactor presubmit jobs to improve cost efficiency and scheduling speed (#3729)

- Remove unused fields and streamline job definitions
- Add run_before_merge to integration jobs to save resource
- Reduce CPU and memory requests for unit-test and build jobs to adjust
the cloud nodes.
- Standardize command definitions for containers
- Trigger unit-test job on default cluster (GCP) to improve scheduling
speed
 (commit: d33a837)