cli/command: remove NotaryClient from CLI interface

[thaJeztah]

cli/command: remove dependency on distribution/uuid

This uuid package was introduced in 89db01e,
but we want to reduce dependency on the old docker/distribution module.

Replace it with google/uuid, which is a commonly used module for this
and already a dependency.

cli/registry/client: remove dependency on trust / notary

The client was only using the Actions consts, but the trust package
also has a dependency on notary. Remove the import to prevent Notary
becoming a dependency for uses of the cli code.

cli/command: remove NotaryClient from CLI interface

This method was a shallow wrapper around trust.GetNotaryRepository, but
due to its signature resulted in the trust package, and notary dependencies
to become a dependency of the CLI. Consequence of this was that cli-plugins,
which need the cli/command package, would also get notary and its
dependencies as a dependency.

Thie patch:

• Removes the NotaryClient method from the interface
• Inlines the code where needed, skipping the wrapper
• Define a local interface for some tests where a dummy notary client was used.

cli/command: remove ManifestStore from CLI interface

This method was a shallow wrapper around manifeststore.NewStore, but
due to its signature resulted in various dependencies becoming a dependency
of the "command" package. Consequence of this was that cli-plugins, which
need the cli/command package, would also get those dependencies.

Thie patch:

• Removes the ManifestStore method from the interface
• Inlines the code where needed, skipping the wrapper
• Define a local interface for some tests where a dummy store was used.

cli/command: remove RegistryClient from CLI interface

This method was a shallow wrapper around registryclient.NewRegistryClient but
due to its signature resulted in various dependencies becoming a dependency
of the "command" package. Consequence of this was that cli-plugins, which
need the cli/command package, would also get those dependencies.

Thie patch:

• Removes the RegistryClient method from the interface
• Inlines the code where needed, skipping the wrapper
• Define a local interface for some tests where a dummy store was used.

- Human readable description for the release notes

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 42.52874% with 50 lines in your changes missing coverage. Please review.

Project coverage is 59.27%. Comparing base (fe0a8d2) to head (685c652).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5876      +/-   ##
==========================================
- Coverage   59.32%   59.27%   -0.05%     
==========================================
  Files         353      353              
  Lines       29748    29791      +43     
==========================================
+ Hits        17647    17659      +12     
- Misses      11113    11145      +32     
+ Partials      988      987       -1