Changes

ci(tiflash-scripts): refine pull regression and schrodinger pipelines (#4480)

## Summary
- use jnlp container in pull_regression_test and pull_schrodinger_test
for checkout stage to avoid the Git working directory from being
corrupted by mixed usage of root and non-root users.

## Files Changed
-
pipelines/pingcap-inc/tiflash-scripts/latest/pull_regression_test/pipeline.groovy
-
pipelines/pingcap-inc/tiflash-scripts/latest/pull_regression_test/pod.yaml
-
pipelines/pingcap-inc/tiflash-scripts/latest/pull_schrodinger_test/pipeline.groovy
-
pipelines/pingcap-inc/tiflash-scripts/latest/pull_schrodinger_test/pod.yaml

## Replay Passed
-
https://prow.tidb.net/jenkins/blue/organizations/jenkins/pingcap-inc%2Ftiflash-scripts%2Fpull_regression_test/detail/pull_regression_test/7/pipeline
-
https://prow.tidb.net/jenkins/blue/organizations/jenkins/pingcap-inc%2Ftiflash-scripts%2Fpull_schrodinger_test/detail/pull_schrodinger_test/8/pipeline

## Use jnlp for checkout
-
https://prow.tidb.net/jenkins/blue/organizations/jenkins/pingcap-inc%2Ftiflash-scripts%2Fpull_regression_test/detail/pull_regression_test/13/pipeline
<img width="1174" height="630" alt="image"
src="https://github.com/user-attachments/assets/b1f01cd0-1613-45a2-931b-cb45bcbb18f6"
/>

---------

Signed-off-by: lyb <yebin.li@pingcap.com>
 (commit: 0f45828)