Consider getting rid of aligned dependency subtree

[nickray]

This eventually pulls in two versions of generic-array which is a bit weird. Maybe take over aligned and/or as-slice and add some feature flags there? Or make itm::write_aligned itself an optional feature?

re. #183

[jonas-schievink]

Oh this is where all the generic-array dependencies come from? I was wondering about that.

Pulling in 4 dependencies for a single function seems very excessive, so I'm on board with removing them. We can add our own alignment-enforcing struct to the itm module instead.

[nickray]

Yeah for some (compatibility?) reason as-slice pulls in both.

[therealprof]

Yeah, otherwise you run into weird compatibility problems.

[nickray]

(Offtopic. None of my dependencies that depend on generic-array use 0.12, so I' be curious what compatibility issues there might be? Is it really not an "alter Zopf"? :) )