Remove path type generic for better ergonomic

[aquarhead]

This could be especially useful when one parameter (e.g. protos) is dynamically collected while the other (includes) is statically defined. Splitting the type should make compile_protos easier to use, I also changed a few instances where type conversion was used to show the impact.

[LucioFranco]

Thanks!

[LucioFranco]

@aquarhead looks like there is a test failure, could you fix that then we can merge this?

[aquarhead]

I'll take a look

[aquarhead]

So seems this will break if includes is empty, it previously works because it uses the type of protos to infer the type of &[]. I'm not sure there's a way to fix this (the type hint requirement)?

It seems this change would improve ergonomics when I have includes but would have the reverse effect when it's empty. Though using &[""] seems to be a workaround.