Ignore blacklisted crates

[brson]

Similar to #99, we maintain a blacklist in blacklist.md of crates with unreliable test suites, but it is not used by cargobomb. Teach cargobomb to ignore these, perhaps by reporting their result as 'blacklisted'.

[aidanhs]

I'd even propose they don't even get tested since some of them generate multiple GBs of output. E.g. we might have a blacklist.toml like:

bad_crate = "*"
other_crate = "0.1.*"

to specify versions of crates to blacklist

Edit: ah I see in the linked issue you are actually suggesting not doing any work for them.

[eddyb]

I have a better idea: have a per-crate "spurious test retry count", such that the crate doesn't show up as failed (at most it shows up as "retried X times") most of the time, without ignoring other causes for failures (e.g. codegen bugs which break the tests consistently).

EDIT: actually, any situation where the succeeded | test-failed | build-failed status is different in before and after, we could automatically retry a few times - they should be in the minority, so not that expensive to do, and would let us triage faster.

[aidanhs]

A brief comment for clarity after talking to @eddyb on IRC: my suggestion for initial blacklist population is for crates that don't work before or after and haven't for (say) three releases. The idea in the comment above is much better for intermittent failures.