Add `is_preview_suffix_enabled` flag to `local_file_volumes` and
`local_persistent_volumes` tables, allowing per-volume control over
whether a `-pr-N` suffix is appended during preview deployments.
Defaults to `true` to preserve existing behavior. Users can disable
it for volumes containing shared config or repository scripts that
should not be isolated per PR.
Bind mount volumes reference files at the repository's original path and
should not receive the -pr-N suffix. Only named Docker volumes require
the suffix for isolation between preview deployments.
Adds PreviewDeploymentBindMountTest to verify the correct behavior.
Fixes#7802