Agdbentures don't crash if engine don't exist. we call make_engine.py before launching level if engine_version is not found. Add an argument in make_engine.py to choose which version we want for the level specified if version is not found to launch faster

Now we can free map and game with the verify exit function because we call them in all levels

i try to remove all leaks of memory in order to use properly our struct in main.c because a lot of malloc are never free

for the first high-level section.
Added options --list and --all to make_engine to respectively only list
versions and generate all versions, including the ones in subsequent high-level
sections (versions that are WIP)

- utils moved from level/utils to loader/loader_utils
- created a prepare_level function
- loading code moved from graphic/window to loader/loader
- test_level function moved to the tests/testLevel script
- window now has a start_level function which is less ambiguous
  than previous load_level function
- cleaned the loading w.r.t. filenames and level names

Added exit_y and exit_x to the first `tests.c` files (first engine versions) to
allow them to compile.
Need to think about how to get these variables to the map struct while not
breaking Agdbentures.

variants return the number of successful moves.
Fix: order of verification in `can_move_to` (check first that we are inside the
map).
Added tests where player tries to get off the map.