Fix TOUCH_SCREEN sleep_timeout_minutes

[thisiskeithb]

Description

Follow up to #26517.

Fix 'DISPLAY_SLEEP_MINUTES' was not declared in this scope error found after running the build_all_examples script.

Requirements

TOUCH_SCREEN with TOUCH_IDLE_SLEEP_MINS

Benefits

TOUCH_SCREEN configs now compile when TOUCH_IDLE_SLEEP_MINS is enabled.

Configurations

• Elegoo/Neptune 2/

Related Issues PR

• Update LCD_BACKLIGHT_TIMEOUT_MINS + small tweaks #26517

[thinkyhead]

Seemed like a good idea to combine the two distinct screen timeout options into a single option and also reduce the number of TERN(TOUCH_SCREEN, ...) instances.

[thinkyhead]

I've consolidated the code a bit further to replace HAS_TOUCH_SLEEP with HAS_DISPLAY_SLEEP and to move the implementations of MarlinUI::sleep_display into each LCD implementation rather than including TFT headers and making special cases within marlinui.cpp. … Just the kind of task that Github Copilot should be taking over some time before the year 2034.

[thisiskeithb]

Unifying display sleep stuff is a good call. I went with the easier route of fixing the build error since I had ~50 configs that weren't building & wanted to get through them without getting sidetracked into why display sleep wasn't a single option 😄