platforms(adaptors): add a generic analog pin adaptor

[gen2thomas]

Solved issues and/or description of the change

Introduce a library at system level for sysfs access. The library is used now for the sysfs digitalpin access, pwm pin access, and a new sysfs analog pin system library.

Based on the library - at adaptor level a new generic adaptor was introduced to access e.g. sysfs in a generic way and be able to implement drivers. Beaglebone and Edison are already converted to use the new base adaptor for its AnalogRead() capability.

Manual test

none

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
• depends on aio(analog sensor): fix deadlock in cyclic reading #1042

If this is a new driver or adaptor:

• I have checked or build at least my new example (e.g. by run make examples_check)