Support pulling known WASI WIT worlds from BCA repositories

[t3hmrman]

Now that BCA tooling (wkg, etc) have evolved to be be able to push/pull OCI artifacts for well known/standardized interfaces from a central location, it would be useful if jco could make use of the known interfaces in jco commands, in particular jco componentize --wit ....

[guybedford]

This would be great to see.

[vados-cosmonic]

Another benefit of this feature (which ideally includes integration of upstream packaging tooling) would be removing wit/deps folders and contents from all examples.