Quiet option to skip validity text

[latot]

Hi all, I think would be great a quiet option for functions like sfnetwork and as_sfnetwork, they actually have this messages:

Checking if spatial network structure is valid...
Spatial network structure is valid

Which can be helpful when we are using sfnetworks manually, but in a lib or tests do the things more complex, if we use a lot of networks to test, we end having a lot of that text all over the place.

There is an option to skip the validation, which is different to this issue, I think the best is be able to run the network validation without this messages, and if is not valid, then throw an error.

Thx!