[Feature request] Changing or disabling LCD Activity timeout

[Julietta]

My main rig is an M3D Crane (effectively an Ender 3 but with a Duet 2 Maestro), and I couldn't figure out how to set the 12864 LCD timeout in it. Poked around the code, it appears to be fixed at 20 seconds in /src/Display/Menu.cpp:81:82 (as of the latest commit, 846c9aa)

const uint32_t InactivityTimeout = 20000;		// inactivity timeout
const uint32_t ErrorTimeout = 6000;				// how long we display an error message for

This really slows down bed leveling as I use macros to put the print head over each bed screw and use a 1mm feeler gauge to adjust it. It's a four-screw bed with nylocs I have to take a 7mm spanner to, so I'm constantly re-entering menus when I bed-level. Would love the option to disable timeout or at least set it unreasonably high so I can avoid it timing out while I bed level.

Being able to adjust error message timeout would be useful as well, my rig sits on the other side of the room from me so I don't necessarily see it quickly enough to know without going into DWC to figure out what I saw, and since they're right in the same area I imagine a fix for one would very readily cover the other.

Any chance of putting this feature on the radar?

Thank you!