Refresh keycloak db env vars

[underq]

Description of the change

Rename database environment variables according to the Keycloak documentation. Source: https://www.keycloak.org/server/all-config?q=db#category-database

Benefits

Use updated configurations in alignment with upstream Keycloak project.

Possible drawbacks

Somes var has been removed, but they were not documented into README.md

[jotamartos]

Thanks for your contribution. Let me sync the changes with our internal repo and I'll merge the changes after that.

[github-actions[bot]]

This Pull Request has been automatically marked as "stale" because it has not had recent activity (for 15 days). It will be closed if no further activity occurs. Thank you for your contribution.

[github-actions[bot]]

Due to the lack of activity in the last 5 days since it was marked as "stale", we proceed to close this Pull Request. Do not hesitate to reopen it later if necessary.