Client-side autojump. Remove Android-only stepheight autojump (#7228)

Works by detecting a collision while moving forward and then
simulating a jump. If the simulated jump is more successful,
an artificial jump key press is injected in the client.

Includes setting and key change GUI element for enabling and
disabling this feature.

builtin/settingtypes.txt

@@ -111,6 +111,10 @@ always_fly_fast (Always fly and fast) bool true
 #    mouse button.
 repeat_rightclick_time (Rightclick repetition interval) float 0.25
 
+#    Automatically jump up single-node obstacles.
+#    type: bool
+autojump (Automatic jumping) bool false
+
 #    Prevent digging and placing from repeating when holding the mouse buttons.
 #    Enable this when you dig or place too often by accident.
 safe_dig_and_place (Safe digging and placing) bool false