Thread-safe access

[bilderbuchi]

Closes #506, supersedes #608.

• Also guard CommonBase.binary_values and binary methods in general
• Need more thread-safety in manipulating ThreadedAccessTester?
• Maybe smoother to fake comms with pyvisa-sim?
• Add tests using many-thread concurrent access without special methods with interrupt points (FakeInstrument? pyvisa-sim?)
• Check if we can monkeypatch out the RLock with some smart fixture use to confirm that all current threading tests that pass with the lock fail without it. This confirms that the tests really catch the threading problems as intended (and don't pass accidentally).
• Add documentation
• Clean up code
• Testing

[bilderbuchi]

@bmoneke I think I need your help -- my tests uncovered that the Keithley2306 Relay (

pymeasure/pymeasure/instruments/keithley/keithley2306.py

Line 577 in 1500e37

class Relay():

) should be a Channel, and also probably that custom Channel (

pymeasure/pymeasure/instruments/keithley/keithley2306.py

Line 33 in 1500e37

class Channel():

) should inherit from the pymeasure one.
I guess we overlooked that one during the Channel transition. Can I fix this quickly without getting bogged down, or is that more restructuring work, in your opinion?

edit: see #953

[BenediktBurger]

I guess we overlooked that one during the Channel transition.

We added channels, but never moved all instruments to channels, see #746