Remove the url crate

[SimonSapin]

The url crate is now deprecated: #16076

It should be removed at some point. How long should be the deprecation cycle?

CC: @alexcrichton, @brson

[alexcrichton]

This crate should remain until at least the 0.12.0 release is out, afterwards I think we can consider doing a deprecation removal sweep.

I think this is now done, closing.