Changes

ci(ticdc): add v7.5.0 and v8.1.0 integration variants (#4304)

## Summary

Add versioned TiCDC integration job variants so CI can test downstream
components with three version lines in parallel:
- existing default line
- v7.5.0 line
- v8.1.0 line

## Changes

- Add 16 Jenkins job DSL entries under `jobs/pingcap/ticdc/latest`:
  - `*_v7_5`
  - `*_v8_1`
- Add 16 matching pipeline directories under
`pipelines/pingcap/ticdc/latest`.
- For all versioned pipelines:
  - use `UPSTREAAM_BRANCH` as version selector variable
  - set version baselines to `v7.5.0` and `v8.1.0`
- Extend `prow-jobs/pingcap/ticdc/latest-presubmits.yaml` with 16 new
presubmits.
- Set `run_before_merge: false` for all newly added versioned
presubmits.

## Testing

- `yq -e '.' prow-jobs/pingcap/ticdc/latest-presubmits.yaml`
- mapping check: each new presubmit has matching job DSL and pipeline
files
- residual check: no `DOWNSTREAM_BRANCH`, `release-7.5`, or
`release-8.1` remains in new versioned pipelines
- `.ci/update-prow-job-kustomization.sh`

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Signed-off-by: tenfyzhong <tenfy@tenfy.cn>
 (commit: 852105e)