Changes

fix(ci): enlarge tidbrelease-8.5 pull_unit_test pod storage (#4543)

## Summary
- increase release-8.5 pull_unit_test workspace and bazel-out volumes to
300Gi
- add a dedicated bazel repository cache mount to match the master job
pod layout
- rewrite Makefile.common repository_cache path so the new cache mount
is used during replay and normal runs

## Verification
- Jenkinsfile validator: `.ci/verify-jenkins-pipeline-file.sh
pipelines/pingcap/tidb/release-8.5/pull_unit_test.groovy`

Co-authored-by: wuhuizuo <wuhuizuo@126.com>
 (commit: 023fbc7)