Migrate argument parsing over to Clap

[mazylol]

Clap is a robust argument parser and it's implementation makes the code a bit more understandable. I see this as a complete win. Additionally, I ran cargo update to get the lockfile modernized. Then I ran cargo-msrv to find the MSRV which then I added to the Cargo.toml + the README. Finally I bumped the version to 1.7.0.

[mazylol]

It would appear that the --locked flag in the action shot me down 😭

[lunacookies]

Thanks for the contribution! We in fact used to use Clap but migrated to a custom argument parsing implementation in #130.

The rationale was that, for our use-case, Clap is quite bloated: at the time switching from Clap to hand-rolled argument parsing reduced our ARM64 macOS binary size from 1.4 MB to 1.0 MB. ARM64 instructions are four bytes each, so we were spending 100,000 instructions (and 29% of the whole binary) just on parsing arguments, which frankly is absurd. Last I checked Clap and its dependencies were around 200,000 lines of code, completely dwarfing not only the ~140 lines of our argument parsing, but also the entire pipes-rs codebase. Clap is so big, in fact, that the people who work on the Rust compiler use it as a compiler stress test.

On top of all that, #130 actually removed more lines than it added!

If you can think of anything that Clap could offer pipes-rs which would be non-trivial to write ourselves, though, then please do let us know. Same for if you spot any other rough edges in the argument parsing behavior :)