Use evaluation when compiling modules

[josevalim]

This explores a different approach to execute module definitions that uses the evaluator (interpreted) rather than the compiler (compiled). I have tried this a long time ago but it was never faster, but I assume a combination of the JIT and different optimizations have made it viable.

Early experiments are very promising. This mode is 5x faster for Remote's codebase compared to 1.19 and 3x faster than main (which already has other improvements:

Version	Elixir Version	Elixir Commit	Total Time	vs Baseline
Baseline	1.19.4-otp-27	N/A	7:47.95 (467.95s)	-
Main	1.20.0-rc.1	426a429	4:57.91 (297.91s)	36.3% faster
This branch	1.20.0-rc.1	732e701	1:25.08 (85.08s)	81.8% faster

The next steps is to expose this as an option and do some additional testing to verify stacktraces are solid. Note this does not change the generated artefact in any way. Each function in the module is still compiled and optimized within the generated .beam file.

[josevalim]

I sent a PR for documentation purposes. I'm not planning to merge it for now.