Use input_manger in worldfactory.cpp

Currently there are ~~3~~ ~~4~~ 5 input systems / functions (maybe more):

- `input_manager` / `input_context` - it seems this is the one to use, right?
- keymap and same functions in action.cpp
- `get_input`, which translates the character that it gets from `getch` to an `InputEvent`, which is just an enum containing a very small subset of possible inputs.
- `getch`, used all over the place.
- `input`, which is another wrapper over `get_keypress`, which is a wrapper over getch. `get_keypress` seems to be actual useful as it removes double keys from the input, and coincidentally it is used by the input manager.

This PR removes `get_input`/`getch` from worldfactory.cpp and uses the `input_context` instead.

Am I right about the preference of the `input_manager`?