Enhance the validation workflow for regoval and celval commands

[santoshkal]

When validation IaC configs using regoval or celval commands a user needs to specify the policy to be used against the config.

Enhance this workflow by following updates:

If a user supplies only a target manifest file and does not provide any policy, Genval should pull the default policies from intelops security policy hub and apply them.

[santoshkal]

The PoC for validating Dockerfiles against a set of Rego policies stored in OCI registries is now available.

Before integrating this functionality into other workflows, such as validating Kubernetes manifests, Terraform files, and CEL policies, the following considerations need to be noted:

• If a user opts to use default policies, Authentication mechanisms must be implemented to interact with registries. This can be documented in command examples and the README file.
• The policy fetching from OCI registries involves an HTTP request-response workflow, which may introduce a delay of a couple of seconds due to the HTTP response, extraction of the tarball, and policy evaluation.
• All URLs for respective policies must be provided to the command through a .env file.

cc/- @devopstoday11