New GitHub Action workflow for on demand commit benchmarking

[rwstauner]

We should add a new workflow (triggered by a UI button):
It will be very similar to the current "benchmark" interface.

Inputs:

• repo
• ref
• build args?
• run args?
• parent/base for comparison
• x86 and/or arm (default both?)

Tasks:

• Setup params (resolve shas for specified ref and parent/base to compare to)
• It should launch a new instance from the AMI
• compile rubies
• run the benchmarks
• upload the json to a bucket
• then it could DM the user (or post the channel) on slack with urls to the json files to notify when complete
• shut itself down

We can leave it there for inspection or further testing if desired.
We could then have a periodic cleaner job that would clean up old instances that have been shut down for 7 days or some other amount of time.

[maximecb]

To simplify the interface, it might be nice if it could just take a commit hash (long or short form), and automatically look for it in ruby/ruby or in Shopify/ruby. People could still optionally specify a repo. Basically just generally have good defaults, and allow starting a run quickly. You only need to specify the full set of parameters if you want to test something specific.

[rwstauner]

Yeah it will take a branch/ref/sha and resolve it in either repo (or another if specified). Everything will have useful defaults