appmap.Recording is available even when APPMAP=false

[apotterri]

Code that imports appmap.Recording should run correctly even when not Env.current.enabled.

I think it should be possible to implement this by creating a new context manager class called _appmap.NoopRecording that gets renamed on import to Recording:

if  _enabled:
    ...
else:
    import _appmap.NoopRecording as Recording