change Erlang code generation

[giacomocavalieri]

With this PR we're switching the Erlang code generation to the current pretty printing approach to a new code generator that is better suited to later be used to produce the binary Erlang Abstract Format!

• This PR changes the Erlang code generator to use a different interface for producing textual Erlang, that is closer reflecting the shape of the Erlang Abstract Form. This is an intermediate step that will allow us to then start generating the EAF binary format rather than textual Erlang files
• This PR closes Use memory arena for pretty printing algebra #2251 as well! Now that the Erlang codegen doesn't need any pretty printing at all I was able to rip out the old pretty module!
• This PR closes let assert with an aliased string prefix pattern generates invalid Erlang #5935 too, changing how let assert expression are compiled
• This PR closes Arguments of integer and float division are evaluated in the wrong order on Erlang #5942 too, changing how int and float divisions are compiled
• This PR closes Redundant warning from Erlang compiler #5962 too, adding the nowarn_ignored compilation flag

[lpil]

Jak this rules!!!

also wow I've never had a worse time with github's UI