Changes

ci(tiflow): migrate release-8.5 ghpr_verify to gcp (#4380)

## Summary
- migrate pipelines/pingcap/tiflow/release-8.5/ghpr_verify.groovy to GCP
- update tiflow pull-unit-test-cdc-8.5 job image to mix Go patch
toolchain artifacts (go1.25.8 vs older go tool) that cause compile
failures

## Replay Test
-
https://prow.tidb.net/jenkins/blue/organizations/jenkins/pingcap%2Ftiflow%2Frelease-8.5%2Fghpr_verify/detail/ghpr_verify/6/pipeline/
-
https://prow.tidb.net/view/gs/prow-tidb-logs/pr-logs/pull/pingcap_tiflow/12566/pull-unit-test-cdc-8.5/2035968598681325568

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Signed-off-by: lyb <yebin.li@pingcap.com>
 (commit: d5da7f6)