PFW-1523 Add a new timer for Prusa Link

[gudnimg]

The idea is to have the host ping the printer periodically with a M79 to enable certain features/UI. Using the usb_timer is not a good solution for this as it depends on seeing a 'G' character

The LCD code, or whatever code is implementing the new functionality will need to include host.h and check whether M79_timer_get_status() returns 0 (timer not running) or 1 (timer is running).

I created a new file for the code host.cpp which we can use to expand host related functionality and not clutter Marlin_main.cpp further.

Some ideas how this could be used (nothing set in stone):

• Show IP address in support menu
• Show "Printer Ready" menu
• Disable or Enable MMU logs or filter them even (unlikely to happen though)
• Different Power Panic behavior
• Lots of ways to render the UI differently e.g. show "PL" instead of "USB" on the status screen.
• Custom Attention messages which should not be used with Octoprint. Messages specific to Prusa Link.
• And so on :)

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TODO

• [x] Implement M79, revert changes in M113
• [x] Implement manage_timeouts() or something in manage_inactivity() which will periodically check if the timer is expired.

[github-actions[bot]]

All values in bytes. Δ Delta to base

Target	ΔFlash	ΔSRAM	Used Flash	Used SRAM	Free Flash	Free SRAM
MK3S_MULTILANG	104	5	246014	5638	7938	2554
MK3_MULTILANG	106	5	245300	5647	8652	2545