Changes

Update memory limit for TiCDC heavy integration test

Increase memory limit from 28Gi to 32Gi to accommodate larger workloads
 (commit: a1020d2)

TiCDC: Update Prow job triggers to remove 'all' keyword and enable run_before_merge for unit tests (#4099)

## Summary

This PR updates the Prow job configurations for TiCDC to refine the
trigger patterns and ensure certain jobs run before merging. The changes
improve the clarity of job triggers and ensure that critical build and
unit test jobs are executed during the pre-merge phase.

## Changes

- **Refined trigger patterns for integration tests**: Removed the `|all`
option from the regex triggers for several integration test jobs in both
`latest-presubmits.yaml` and `latest-presubmits-next-gen.yaml`. This
ensures that these jobs are only triggered explicitly by their specific
command or the `next-gen` keyword (where applicable), reducing
unnecessary runs and improving trigger precision.
- **Updated `pull-unit-test` job**: Commented out `skip_if_only_changed`
and added `run_before_merge: true` to guarantee unit tests are executed
before merging, enhancing code quality assurance.

## Why These Changes?

- **Trigger clarity**: Removing the `all` keyword from triggers prevents
unintended job executions when using the `/test all` command, aligning
triggers with specific job intents.
- **Pre-merge reliability**: Ensuring `run_before_merge` is set for
build and unit test jobs guarantees these critical checks are always
performed before code is merged, maintaining stability and preventing
regressions.
- **Consistency**: The updates apply to both the current and
next-generation Prow configurations, ensuring uniform behavior across
job suites.

## Closed Issues

N/A

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Signed-off-by: tenfyzhong <tenfy@tenfy.cn>
 (commit: 6ce7710)