RTA not mandatory

This series allows nitg-e to not depends on RTA to compile.

The three difficulties where:

1. RTA can issues somme errors early, so disabling it changed some tests results. This is fixed by the 3 first commits
2. RTA is required in abstract_compiler, so the 2 next commits make it not mandatory (nullable) even if giving NULL will yield some NPE errors, because
3. RTA is used to collect what super-calls exists so they can have slots in the method tables. The 6th commit offers a new analysis `collect_super_sends` to do the job when RTA is not available

The last two commits just enable nitg-e to run without RTA and update the test `base_gen_infinite` that now works with nitg-e!