Add most of the EPC_BGA-0.9x0.9mm symbols

Add most of the EPC_BGA-0.9x0.9mm symbols

Footprint MR: kicad-footprints!3424 (merged)

This MR includes several parts at once, because they all derive from one symbol (EPC2035) and have the same footprint. For the symbol of EPC2035, I simply copied the already existing symbol of GS66508B and modified it.

The freewheeling diode which is depicted in the symbol of the datasheet is actually misleading. GaN HEMTs like the ones from EPC (and GaN Systems) have no body diode. They have a mechanism which is called "self-commutated reverse conduction characteristics". Also see: https://epc-co.com/epc/Portals/0/epc/documents/papers/eGaN%20FET%20Electrical%20Characteristics.pdf (look for explaination of "Vsd" on p.3). Therefore, I decided to take the GS66508B symbol.

Datasheets:

EPC2035: https://epc-co.com/epc/Portals/0/epc/documents/datasheets/EPC2035_datasheet.pdf

EPC2036: https://epc-co.com/epc/Portals/0/epc/documents/datasheets/EPC2036_datasheet.pdf

EPC2037: https://epc-co.com/epc/Portals/0/epc/documents/datasheets/EPC2037_datasheet.pdf

EPC2038: https://epc-co.com/epc/Portals/0/epc/documents/datasheets/EPC2038_datasheet.pdf

EPC2203: https://epc-co.com/epc/Portals/0/epc/documents/datasheets/EPC2203_datasheet.pdf

EPC2219: https://epc-co.com/epc/Portals/0/epc/documents/datasheets/EPC2219_datasheet.pdf

New symbol:

For reference, GS66508B symbol: