code reduction & cleanup

[digant73]

Once the code is pretty stable since some time now, scope of this PR is an overall cleanup and code reduction (no code is changed).

IMPROVEMENTS:

• Code reduction: with the exception of 3rd party libs (e.g. ST, GD libraries etc.), static and static inline qualifiers has been applied for local-scope variables and functions (best practice) allowing a reduction of about 800 bytes on flash usage.
• Cleanup: with the exception of 3rd party libs, an overall cleanup has been applied. No code was changed, only some functions and declarations/definitions moved or ordered from .h to .c when possible.
• Some bugfixes on last integrated GD32F30xx API (used by recent MKS TFT28 variants):
  • UART ports set to 5: 6 UART ports have been previously defined but only 5 could be available/initialized (6th port _USART6 was present but not initialized in uart.c).
  • RAM size set to 96KB: RAM size was previously set to 64KB in gd32f30xxC_0x7000_iap.ld file.

PR STATE: Ready for merge

[rondlh]

Changed 281 files, amazing!!! Well done like always.

Tiny issue: in User\Menu\ScreenSettings.c, line 19

static const char * const labelMarlinType[ITEM_MARLIN_TYPE_NUM] =
{
  // item value text(only for custom value)
  "128x64",
  "20x4"
};

This is only needed if the emulator is enabled, so probably best to guard it (#ifdef HAS_EMULATOR) or push it down to the HAS_EMULATOR section.

[digant73]

yes, I will apply the filter on the next PR (I will complete the cleanup)