Add docker_manifest_lists endpoint

[vsedmik]

Description of changes

Just adding the docker_manifest_lists endpoint to the Repository class.

Upstream API documentation, plugin, or feature links

https://<SAT_FQDN>/apidoc/v2/docker_manifest_lists/index.en.html

Functional demonstration

In [1]: from robottelo.hosts import Satellite

In [2]: sat = Satellite('satellite.redhat.com')

In [3]: sat.api.Repository(id=77).docker_manifest_lists()['results'][0]
Out[3]: 
{'id': 3,
 'schema_version': 2,
 'digest': 'sha256:a3279836b6154516cae3b972fba258e7e202b73454c1cdd73a8d98306cf35a51',
 'manifest_type': 'list',
 'annotations': {},
 'labels': {},
 'is_bootable': False,
 'is_flatpak': True,
 'tags': [{'id': 3, 'repository_id': 'CqRPYqstzg', 'name': 'latest'}],
 'manifests': [{'id': 3,
   'digest': 'sha256:f440f187a3792844892f231b5fc15e3a1636c3bc5e82ea6a29b5eb0cc93750b2',
   'schema_version': 2,
   'manifest_type': 'image'},
  {'id': 4,
   'digest': 'sha256:5140ab5963bc73b2be189fa32b1122568fbbb0351913a47ab5a6386b6dd82fa3',
   'schema_version': 2,
   'manifest_type': 'image'}]}

Additional Information

For the Functional demonstration just sync some container repo. I used these:
https://github.com/SatelliteQE/robottelo/blob/d1efa751f931d249731aa7d9a1702e23818d9eb9/robottelo/constants/__init__.py#L729

[LadislavVasina1]

LGTM