fix: cleanup some unnecessary dependencies

[Nicceboy]

Fixes #359

Seems like rayon is only used for processing constraints in parallel and typically the amount of constraints is rather small.
I could not measure any drastic performance difference when compiling whole workspace, so I just removed rayon:

# With rayon
cargo build --workspace --all-targets  142.49s user 17.37s system 742% cpu 21.517 total

# Without rayon
cargo build --workspace --all-targets  141.91s user 17.11s system 752% cpu 21.136 total

Also arrayvec has been removed as I could not find any usage for it.

There is constant equivalent for current konst dependency usage, so this removes that as well.

[Nicceboy]

I also removed the macros feature since it is not currently possible to compile rasn without it. Or should we rework Open type before doing so?

[XAMPPRocky]

Thank you for your PR!