refactor: new rawsmallvec representation

[alejandro-vaz]

this PR is a draft

closes #583

closes #441

[alejandro-vaz]

will solve it tomorrow

[fereidani]

Hey Good Idea but this 5 lines kept repeating in the changes:

          if on_heap {
              self.raw.as_heap()
          } else {
              self.raw.as_inline()
          }

Why not use a refactored/compatible as_ptr(on_heap) and as_mut_ptr(on_heap) instead?

[alejandro-vaz]

yeah I haven't done that yet, I wanted to first do it that way and check it works

doing so that way erases the length of the array on type data on the inline variant so I was pretty reluctant to do so at first

[alejandro-vaz]

great... I killed something and I don't know why

[alejandro-vaz]

I need a few more days for this

@fereidani this is a bombshell to how we represent the rawsmallvec, would be grateful I you could provide integration support to make sure that this lands correctly

just fixed a bunch of test errors because of some mistake I made whilst remaking try_grow_raw

[fereidani]

Sure thing, Let me know where I could help.