Bugfixes on top of last merged PR

[digant73]

BUGFIXES:

• Fixed TFT35 freezes before Purging #2895: Bug introduced by Added Command Checksum + code optimization + cleanup #2889 and affecting TFT variants with a LED on knob (e.g. TFT35 E3 V3.0 etc.) in case knob_led_idle setting on config.ini file was enabled. The bug caused a freeze exiting from PID/MPC menus or during the Event LED process, if enabled, at the beginning of a print. The bug was due to the missing volatile qualifier on ms attribute of OS_COUNTER data struct.
  NOTE: The bug severity can be considered major for the affected TFT variants
• Fixed [BUG] Preheat: name can causes the menu to freeze requiring a restart. #2898: Bug causing a freeze entering on Preheat menu. The bug was present in case the names (e.g. Poly Carbonate etc.) defined in config.ini file required a pixel width wider that the underlying icon image displayed on the screen.
• Fixed missing default initialization on flash for preheat names and temperatures: Bug fixed in Config.c
• Minor cleanup

PR STATE: Ready for merge

fixes #2898
resolves #2896 (answer provided. Not an issue on TFT)
fixes #2895
resolves #2880 (tested and properly working. Not an issue on TFT (used wrong TFT fw or TFT resources)
resolves #2875 (answer provided. Not an issue on TFT)
resolves #2853 (zombie. Feedbacks provided but no more reply)
resolves #2821 (answer provided (very old TFT fw (2019) needed to be updated)
resolves #2796 (zombie)
resolves #2734 (answers provided)