Add ucd crate

[lqd]

As seen in rust-lang/rust#53643, this crate has big statics similar to html5ever, but different enough that it's still an NLL stress test.

@nikomatsakis mentioned we should add it to perf in this comment.

[Mark-Simulacrum]

Can you add a perf-config.json file with these contents? That way it'll take up less time on the benchmark machine.

{
    "runs": 1
}