Separate pressing Enter to open map from pressing Enter to interact

This is a lot of copy-pasted code, but a little bit of copy-pasting
never hurt anyone...

The keybind to interact with activity zones and teleporters is now
separate from the keybind to open the map, or return to the editor from
in-editor playtesting, or restart a time trial. The keybind is now E,
and the default controller bind is X. No controller button prompts, but
the game didn't have controller button prompts anyways, so whatever.

Doing this now because if people's muscle memory are going to be broken
by not being able to spam the map keybind anymore, at least we can help
a bit by changing the keybind so they can keep spamming it - their
muscle memory is going to be broken anyways.

This option has to be enabled by going to the speedrunner menu options
and selecting "interact button". It is disabled by default.

All prompt text needs to be string-interpolated every time they are
drawn, because it is possible for people to change which interact button
they use in the middle of gameplay, via the in-game options.

Closes #736.

desktop_version/src/KeyPoll.h

@@ -19,6 +19,7 @@ enum Kybrd
 	KEYBOARD_s = SDLK_s,
 	KEYBOARD_a = SDLK_a,
 	KEYBOARD_d = SDLK_d,
+	KEYBOARD_e = SDLK_e,
 	KEYBOARD_m = SDLK_m,
 	KEYBOARD_n = SDLK_n,