Add support for recommended_deployment fields and automatically uncompress gzipped artifacts

This release includes two bug fixes that fix gaps between the API specification and implementation.

• #459 ensures that the recommended_deployment field of APIs is stored and returned as specified in the API protos.
• #457 ensures that artifacts stored with gzip compression (as noted in their mime types) are automatically decompressed by the handler of the GetContents method as described [in the API protos].(https://github.com/apigee/registry/blob/61c5bc7df3a3ddbdb9587ae184b5d26a2931b39e/google/cloud/apigeeregistry/v1/registry_service.proto#L328).

Additionally in the registry-server,

• #461 contains a database performance improvement contributed by @maghasemzadeh.

On the client side,

• #458 adds missing support for setting labels and annotations on Deployment resources using the registry tool.
• #456 causes generated clients to automatically retry DeadlineExceeded gRPC errors.