List bundle dependencies

**Describe the problem/challenge you have**
***List dependencies:***
An imgpkg bundle can either be a standalone bundle or a package repository, with them referencing dependent artifacts which can either be OCI artifacts or other imgpkg bundles. The imgpkg CLI today does not provide an option to query a bundle to list all dependent artifacts (regardless of the level of nesting) without doing a pull and parsing through the contents of the bundle.

This requires knowing the internals of the imgpkg bundle layout which is an implementation detail and causes too tight a coupling for clients consuming the CLI.

This feature is very helpful to inspect contents of the bundle metadata without requiring to download it, similar to how artifact manifest can be inspected using the crane command.

**Describe the solution you'd like**
Provide a CLI option and an API to allow clients consuming the bundles to query for all dependent artifacts and their types (bundle, repo, image) with their references locked to the relocated repository, similar to how “imgpkg pull” would fix the images lock.

Example:
`imgpkg -b --list-deps`
returns images referenced after the images are locked
`Images referenced in the ImagesLock of the bundle:`
`index.docker.io/test/package-repo@sha256:b5e1cfb8731bf5ba6a0fb7060c37bbca03e9fb12be56dbec4a1fe2bbdfff2bd3`
`index.docker.io/test/package-repo@sha256:42030f63b66e25a03c7d9ef28fa5369d230df5697b4ab2d94860e3f69026d18a`

**Anything else you would like to add:**
None

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