Support for Registry

### Description

Please add support for AgentCore Registry to create Registry and creating, approving, listing, and searching registry records for the registry in the agentcore cli. This would help agent developers and CI/CD pipelines to publish the tools, skills and agents to the registry.

### Acceptance Criteria

agentcore cli command provides option to create registry, then add, approve, list and search registry records to the registry.

### Additional Context

_No response_

Start by reading the agentcore CLI's existing command structure and patterns for interacting with services. The issue names no files or tests, so first locate where CLI commands are defined and how they are tested. Done means the CLI supports creating a registry and creating, approving, listing, and searching its records.

Written by the indexing model from the issue text.