Support OPA bundles or imports

Support OPA bundles or imports.

Our use case is we currently leverage "utility" rego's to share functions between policies.

As Spacelift plan policies do not support this, it means duplicating code across policies.

Additionally, having specific plan policies i.e. a one for dynamo, a one for s3 etc, clutters the UI.

Ideally, if we could provide a bundled library of policies, it would save such clutter on the UI.

https://www.openpolicyagent.org/docs/latest/cli/#synopsis-1 https://www.openpolicyagent.org/docs/latest/policy-language/#imports