Create PACs for the RISC-V low-power coprocessors

[jessebraham]

The ESP32-S2/S3 have a rather limited RISC-V ULP core, where as the ESP32-C6 has a much more capable RISC-V LP core.

• ESP32-C6
• ESP32-S2
• ESP32-S3

[jessebraham]

ESP32-S2/S3 added in #136

[jessebraham]

ESP32-C6 added in #137