Deprecate the url crate.

The replacement is [rust-url](https://github.com/servo/rust-url),
which can be used with Cargo.

Fix #15874
Fix #10707
Close #10706
Close #10705
Close #8486
auto merge of #16076 : SimonSapin/rust/deprecate-url, r=alexcrichton

The replacement is [rust-url](https://github.com/servo/rust-url), which can be used with Cargo.

Fix #15874
Fix #10707
Close #10706
Close #10705
Close #8486