feat: enable listing with cargo-nextest and a timeout

[Ekleog-Polygon]

Builds on top of #289, review only the second commit to see the changes introduced here.

This allows using nextest with a specific nextest profile, instead of cargo test. In particular, with this nextest configuration:

[profile.list-fuzzers]
slow-timeout = { period = "500ms", terminate-after = 1 }

I'm getting the following improvements on listing fuzzers for https://github.com/agglayer/agglayer.
Before:

cargo  57.07s user 10.98s system 92% cpu 1:13.75 total

After:

cargo  8.38s user 3.77s system 47% cpu 25.509 total

Which is a ~3x speed improvement, without any fuzzer being missed (because fuzzers naturally reply to CARGO_BOLERO_SELECT in less than 500ms) 🎉

I'm thinking this could be very helpful for large repos, at least until something like #196 could get implemented.

WDYT?