Changes

feat(tidb): add ddlv1 unit test pipeline (#3150)

This pull request introduces a new Jenkins pipeline job for running unit
tests on the latest version of the `pingcap/tidb` repository. It
includes the creation of the pipeline job, its definition, and updates
to the relevant presubmits configuration.

### New Jenkins Pipeline Job:

*
[`jobs/pingcap/tidb/latest/pull_unit_test_ddlv1.groovy`](diffhunk://#diff-1774a984294d89d34230774eb9ef00228b3ff3aecda9adc1e48adf624c810bb8R1-R38):
Added a new pipeline job definition for
`pingcap/tidb/pull_unit_test_ddlv1`, including parameters, properties,
and SCM configuration.
*
[`pipelines/pingcap/tidb/latest/pull_unit_test_ddlv1.groovy`](diffhunk://#diff-5bba6bdccf3d6f4b2c714649e73aa7e35188dda4e40683190e0e2fbb8b4b573cR1-R75):
Implemented the pipeline script for the new job, setting up Kubernetes
agents, environment variables, and stages for debugging, checkout, and
testing.

### Presubmits Configuration:

*
[`prow-jobs/pingcap/tidb/latest-presubmits.yaml`](diffhunk://#diff-35ccc0efb0c9d75d84787908ce4f772045178169d13836c8b429bfed39b986d6R54-R65):
Added a new presubmit configuration for the
`pingcap/tidb/pull_unit_test_ddlv1` job, including branches, trigger
commands, and context settings.Add a new pipeline foro ddlv1 unit test,
we need to monitor the stability of the new pipeline, only support
trigger manually currently.
 (commit: 67eb6f5)