Make jog parameter variables global

[patryk3211]

This PR makes the jog_distance and jog_feed globally accessible. My use case for this is to allow hardware buttons to use the same jogging parameters as set in the menu. Please let me know if this is fine or if these should stay static.

[Paciente8159]

I guess it's ok to allow using the built in jog callback

[Paciente8159]

I propose to rename the variables to g_system_menu_jog_distance and g_system_menu_jog_feed.
This way it will be more meaningful

[patryk3211]

Done