Run cargo clippy in servo repos

[sagudev]

Currently only servo/servo runs clippy and deny warnings. I suggest we enable this for other repos as well. This can cause additional maintenance burden and occasional breakage on new rust releases (weekly runs to detect this?). Any opinions?

[jdm]

I'm ok with that, but I'd recommend starting with one or two repos that are currently receiving attention and then filing an issue tracking the remainder that can be worked on incrementally by new contributors, using the firat ones as a model.

[jschwe]

We should pin the checks by setting either clippy version or the rust-version in the cargo.toml. this way lints must be explictly updated to a newer toolchain instead of automatically whenever a new release appears.

[nicoburns]

Yeah, we'll definitely want to pin the clippy version for this. I generally don't do this in smaller projects, but we can't be updating clippy lints for 150 repos every 6 weeks.