Changes

ci: speed up pipeline verify (#3573)

This pull request introduces improvements to the Jenkins pipeline
validation process by refactoring scripts and enhancing parallel
execution. Key changes include the creation of a dedicated script for
validating individual pipeline files, optimizing the main validation
script with parallel processing, and updating the presubmit
configuration to install necessary dependencies.

### Refactoring and script optimization:

*
[`.ci/verify-jenkins-pipeline-file.sh`](diffhunk://#diff-9638134718b6f8f0c0ad2698a0b232bec3329affb66708ebb0d5d02f9aa3b123R1-R19):
Added a new script to validate individual Jenkins pipeline files using
the REST API. This modular approach simplifies the main validation
logic.
*
[`.ci/verify-jenkins-pipelines.sh`](diffhunk://#diff-7e0d28f8890bf0263059e0a35621ced5c1c7eb8bd3f7079827bd84854a99a8c1L1-R3):
Refactored the script to use the newly created
`verify-jenkins-pipeline-file.sh` for file validation. Added support for
parallel execution using the `parallel` command if available, improving
performance when validating multiple files.
[[1]](diffhunk://#diff-7e0d28f8890bf0263059e0a35621ced5c1c7eb8bd3f7079827bd84854a99a8c1L1-R3)
[[2]](diffhunk://#diff-7e0d28f8890bf0263059e0a35621ced5c1c7eb8bd3f7079827bd84854a99a8c1R12-R20)

### Presubmit configuration updates:

*
[`prow-jobs/pingcap-qe/ci/presubmits.yaml`](diffhunk://#diff-9db5df27906664c96b24883b91f2527720f4898654f108244cda91118a5e9d4aL17-R21):
Updated the presubmit job configuration to install the `parallel`
package before running the validation script. This ensures compatibility
with the optimized script.

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Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
 (commit: 62c8953)