feat: parallel iterations and sorting using rayon

[somehowchris]

It's a fact that crates.io is growing and a crate like cargo-watch already has 57 versions. I know the rust community is split about the use of rayon in many cases. I know it doesn't have a huge impact for this crate, but why not benefit from it anyways?

Some for loops can just not be parallelized as they are printing out statements in certain orders, nevertheless things like version selection do see a benefit. i.e. of cargo-watch I do see a reduction of min 200ms on my machine.

If I know if #130 makes it, I could try to implement it in its extraction

[ryankurte]

once again i appreciate the PR, but short of a demonstrated need would prefer to minimize complexity / dependencies. if you have ideas like this you're welcome to open an issue (or post on the meta-issue) prior to implementation to gauge the response before spending the time ^_^

[somehowchris]

Sure, well again It's not my project so these are just my suggestions. Things like https-only and aarch64 support which have a history, may break some things or are known to be hard, sure I saw a reason to open a ticket as its not just a 10 min implementation. This and #131 were more or less just hit or miss. I do see a benefit for this going onward and in backoff for things like working from a (**** word for not that great) wifi and behind proxies/shared infra where sometimes I have to retry.

Well, let me know if I should open an issue for them or if you see them as "done"?