core(system): split system accesser features

[gen2thomas]

Solved issues and/or description of the change

Applying some system options was complicated. This means the right position in code to apply the option was not clearly visible and how to bubble/chain options from user to the system was complicated. Additionally each adaptor was build with all system access features, although they are not supported by the adaptor.

Additionally:

• change functional options of system layer from function style (system.Optioner) to applier style (system.AccesserOptionApplier)
• simplify option handling of digital pin adaptor, added in one of the former PR's
• introduce options for SPI adaptor
• move implementation for "WithSpiGpioAccess" from digital pin adaptor to SPI adaptor
• prepare platforms without native SPI support (chip, dragonboard, etc.) to be able to use "WithSpiGpioAccess"
• increase test coverage and fix findings (e.g. calculation of tclk in spi_gpio.go)
• add debug flag in config for SPI and digital pin adaptor, provide this flags to system layer
• fix some findings regarding wrong file names (try to apply common go style)

Manual test

• OS and Version (Win/Mac/Linux): Linux
• Adaptor(s) and/or driver(s):
  • nanopi NEO (digital pin)
  • Tinkerboard 2 (i2c)

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