Add missing STMicroelectronics STM32 microcontroller footprints

This MR goes along with kicad-symbols!3559 (merged)

This MR adds all missing packages for ST's current STM32 microcontroller lineup.

For some of these packages, I had to extend the BGA/CSP footprint generator. The new features are:

• New shorthands for pin skipping;
  • List of named pins, like [A1, B17, C38]
  • Rectangular area, like [D, 1, J, 8] will skip everything in the rectangle with top left corner D1 and bottom right corner J8 (including both corners)
  • Checkerboard shorthand for staggered pin arrangements in WLCSPs: checkerboard_skip: A1 will skip every even-index pin, and with A2 or B1 it will skip every odd-index pin. This saves a bunch of time writing out every second pin index for large staggered layouts.
• Support for pin arrays that are offset from the package's true center
• Support for multiple grids per package
  • Combined with area skips, this allows the specification of BGAs that have a grid with one pitch nested inside a ring of pads with another pitch. Examples are the new TFBGA-361, TFBGA-257 packages also introduced with this MR.

X-ref MR against footprint library repo: kicad-footprints!2924 (merged)