slapos cli: add slapos cachelookup commands
This commit remove the following 2 commands:
- slapos cache lookup
- slapos cache source
And introduces the following 3 commands:
- slapos cachelookup binary-sr
- slapos cachelookup url
- slapos cachelookup pypi
This is useful to check if some objects are in shacache for buildout. Please note that the commands are using the latest keys (introduced in slapos.buildout!26 (merged))