Move to updated Elixir and Erlang versions

[devonestes]

No description provided.

[PragTob]

Thanks!

Seems like we have some legit memory failures and I think we might need to exclude 1.4/1.5 for OTP 21.

[PragTob]

Yeah memory measurements somehow break... the old scenario from @michalmuskala (that we gladly tested) breaks and so does some simple stuff like: fn -> Enum.map([1, 2, 3], fn i -> i + 1 end) end

It gets exactly the same heap information before/after... which makes no sense unless this scenario is now optimized/inlined as well:

[
  old_heap_block_size: 0,
  heap_block_size: 233,
  mbuf_size: 0,
  recent_size: 0,
  stack_size: 13,
  old_heap_size: 0,
  heap_size: 220,
  bin_vheap_size: 0,
  bin_vheap_block_size: 46422,
  bin_old_vheap_size: 0,
  bin_old_vheap_block_size: 46422
]
[
  old_heap_block_size: 0,
  heap_block_size: 233,
  mbuf_size: 0,
  recent_size: 0,
  stack_size: 13,
  old_heap_size: 0,
  heap_size: 220,
  bin_vheap_size: 0,
  bin_vheap_block_size: 46422,
  bin_old_vheap_size: 0,
  bin_old_vheap_block_size: 46422
]

(also no memory collected)

[PragTob]

Still pushed my upgrade to remove the unfitting builds from the built matrix... leaving this alone again now because the 3 failures seem hard to figure out :(

[PragTob]

In case anyone sees this and thinks wtf they aren't working on this... we are but it's hard and we're scratching all our heads.

[PragTob]

Ok the memory measurement problems exist whether we merge this or not... I think we'll skip the problematic tests on OTP 21 until we merge them :)