gpio(adaptors): fix so now gpiodev is used as default

[gen2thomas]

Solved issues and/or description of the change

#1109

This means:

• using the gpiod implementation is now the default for new platforms
• behavior can be changed by the user with "adaptors.WithSysfsAccess()"
• platforms which do not have translation maps for gpiod are forced to use the legacy sysfs, so this is a compatible change
• unit tests for gpiod pins can use the "system.UseMockDigitalPinAccess()"

Additionally:

• switch from "Optioner" to "Applier" implementation for digital pin options
• simplify analog pin definition map a bit
• increase test coverage

Manual test

• OS and Version (Win/Mac/Linux): Linux
• Adaptor(s) and/or driver(s):
  • Nanopi NEO (gpiod) - example "nanopi_direct_pin.go"
  • PocketBeagle (sysfs) - new example "beaglepocket_direct_pin.go"

Checklist

• The PR's target branch is 'hybridgroup:dev'
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes (e.g. by run make test_race)
• No linter errors exist locally (e.g. by run make fmt_check)
• I have performed a self-review of my own code