WIP: Rust score calculation

[nicoburns]

THIS PR IS NOT INTENDED FOR MERGING IN IT'S CURRENT FORM

• Work towards fixing Rewrite score calculation in Rust #25

Actual score calculation is implemented in the wptreport crate:

• https://crates.io/crates/wptreport
• https://github.com/nicoburns/wptreport

This PR adds a CI job to run the CLI from the crate on Github CI here with the purpose of seeing how fast the code runs on GIthub Actions.

[nicoburns]

Ok: this PR is doing score recalculation in 2m 49s vs. 27m 8s on main. That's a pretty nice improvement!

[mukilan]

The numbers look really promising! I've given the crate only a cursory read through - it seems like if the goal is to use this for Servo's WPT dashboard, the pending items are

• A way to recalculate past runs by scoring them against a given run.
• Support regex based areas to support /css/CSS2/tables & /css/css-tables. Doesn't have to be regex, I guess, we just need a way to combine arbitrary folders.
• Few unit tests for confidence. Maybe just generating scores.json against a fixed dataset using the crate and diffing it against the current one would also work.