feat(sentry): add db cleanup

[TartanLeGrand]

This pull request adds support for automated database cleanup of the nodestore_node table in Sentry's Helm chart. It introduces a new configurable cron job that performs SQL deletion and vacuuming to reclaim space, with options for scheduling, resource management, and environment setup. The changes are documented in the chart's README and are configurable via values.yaml.

Database Cleanup CronJob Feature:

• Added a new cron job template (cronjob-sentry-db-cleanup.yaml) that runs SQL commands to delete old records and vacuum the nodestore_node table, with support for scheduling, resource limits, and environment variables.
• Introduced new configuration options in values.yaml under sentry.cleanup.dbCleanup to control the cron job's schedule, image, resources, and other settings.
• Updated the README to document all new dbCleanup configuration options for users.

Environment Variable Handling:

• Added a helper template (sentry.postgresql.env) to correctly set PostgreSQL environment variables for the cleanup job, supporting both internal and external database secrets.

[Mokto]

The tests are failing ;)