use const_generics for AlignedArray once it hits stable

[lu-zero]

• Replace the ARRAY generic with with a generic type bound over const N: usize and T
  • Potentially restrict it to only Copy types
• Add an init_slice_mut() method
  • Replace the usage of init_slice_repeat_mut

See: rust-lang/rust#44580

[FreezyLemon]

Is this issue still relevant? I can't seem to find this AlignedArray type anywhere in the code.

EDIT: Nevermind, I figured it out. AlignedArray got renamed to just Aligned at some point. I will take a look at this

[lu-zero]

We should revisit when the MaybeUninit methods specific for array hit stable, I guess