Build/Test Tools: Update third-party GitHub Actions.

This updates the following GitHub Actions:

- `actions/cache` from `4.3.0` to `5.0.3`.
- `actions/checkout` from `5.0.0` to `6.0.2`.
- `actions/download-artifact` from `7.0.0` to `8.0.1`.
- `actions/setup-node` from `6.0.0` to `6.3.0`.
- `actions/upload-artifact` from `6.0.0` to `7.0.0`.
- `ramsey/composer-install` from `3.1.1` to `4.0.0`.
- `shivammathur/setup-php` from `2.35.3` to `2.37.0`.
- `slackapi/slack-github-action` from `2.1.1` to `3.0.1`.

See #64227.

git-svn-id: https://develop.svn.wordpress.org/trunk@62033 602fd350-edb4-49c9-b593-d223f7449a82