Add Support for GigaDevice GD32F and GD32E chips

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• Feature Request.
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  already exists! Don’t send pull requests to implement new features without first getting our
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See https://www.gigadevice.com/products/microcontrollers/gd32/ and catalog for GD32 ARM-type chips. GD32V (RISC-V based) chips are already supported, but not the GD32F (Cortex-M3 and Cortex-M4) and GD32E (Cortex-M23, Cortex-M33 and entry-level Cortex-M4).

The chip vendor supplies its own STM32-like Simple Peripheral Library (SPL) framework as development tool, see http://www.gd32mcu.com/en/download/7?kw=

I currently support the GD32F130C6 and -C8 versions at https://github.com/maxgerhardt/pio-gd32f130c6 with the vendor's SPL pacakge, as maxgerhardt/framework-spl@2.10301.0 (aka combination of GD32F1x0_Firmware_Library_v3.1.0 and GD32F10x_Firmware_Library_V2.1.2 from vendor), and the GD32F103RC chip (with the same SPL version) under https://github.com/maxgerhardt/pio-gd32f103, but official support would be good.

I don't fully understand the chips but it might be that the GD32F103xx chips are exact clones of the STM32F103x chips, which also means they would implicitly be supported by the Arduino-STM32 core. For other chips like the GD32F130x series, I did not find a correlation.

Start by reviewing the existing GD32V support and the linked GD32F130C6, GD32F103, Arduino-STM32, and vendor SPL references. Determine the scope of official support for GD32F and GD32E families, then verify that the supported chips build using the vendor's SPL framework.