raspi(pwm): add support for sysfs and fix pi-blaster

[gen2thomas]

Solved issues and/or description of the change

solve/fix #1032 , additionally:

• switch jetson nano to use default sysfs-PWM adaptor
• use "inversed" as default value for inverted polarity since newer Kernels use this value instead of "inverted"
• introduce validation of calculated duty cycle (rate)

Manual test

• OS and Version (Win/Mac/Linux): Linux (raspios, bookworm)
• Adaptor(s) and/or driver(s): raspi rev0 model B with
  • sysfs-PWM & Servo/Motor (using "pwm0")
  • pi-blaster & Servo/Motor (using header pin 7 = GPIO4)

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)
• No linter errors exist locally (e.g. by run make fmt_check)
• I have performed a self-review of my own code

If this is a new driver or adaptor:

• I have adjusted the corresponding README.md for usage of pi-blaster
• I have added an example to see how to setup and use it
• I have checked or build at least my new example (e.g. by run make examples_check)