Support crates option to run on only the crates with errors from a previous run

[joshtriplett]

The crates option supports an explicit list of crates. For convenience, it'd be nice to have an option that takes a previous crater experiment and runs crater on only the crates failed from that previous run.

[Skgland]

Each crater run already generates a retry-regressed-list.txt with all (spurious-)regressed crates e.g. https://crater-reports.s3.amazonaws.com/pr-135073/retry-regressed-list.txt which is listed near the bottom of the crater reports download tab.
An example of how to use that can be seen here rust-lang/rust#134688 (comment)

[joshtriplett]

@Skgland Helpful, thank you!

I do still think it'd be convenient to have a craterbot syntax that automatically uses that, though, to simplify iterating on a crater run to eliminate regressions.