Prepare for OTP 28

[wojtekmach]

OTP 28 is using a new regexp engine, PCRE2. Prior to OTP 28, Erlang regexps were using a binary:

iex> ~r// |> Map.from_struct()
%{
  re_pattern: {:re_pattern, 0, 0, 0,
   <<69, 82, 67, 80, 71, 0, 0, 0, 0, 0, 0, 0, 1, 128, 0, 0, 255, 255, 255, 255,
     255, 255, 255, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 64, 0, 0, 0, 0, 0, 0, 0,
     0, 0, ...>>},
  opts: [],
  source: "",
  re_version: {"8.44 2020-02-12", :little}
}

Now it's:

iex> ~r// |> Map.from_struct()
%{
  re_pattern: {:re_pattern, 0, 0, 0, #Reference<0.3488040677.452067330.62636>},
  opts: [],
  source: ""
}

Having reference as part of term is problematic, this now crashes during compilation:

defmodule Main do
  @regexp ~r//

  def main do
    @regexp
  end
end

** (ArgumentError) cannot inject attribute @regexp into function/macro because cannot escape #Reference<0.3597165861.3136946177.250217>. The supported values are: lists, tuples, maps, atoms, numbers, bitstrings, PIDs and remote functions in the format &Mod.fun/arity