add phlsys_tracedecorator for testing and debug

Move the 'logging decorator' from it's temporary home in abdt_branchmock
to a permanent home in phlsys.

Allow easy tracing out of method parameters and return values for speedy
debugging of mock and other objects in unit tests.

Test Plan:
Manually inspect unit test trace
$ ./precommit.sh
Arcyd: check conduitmock matches via dict not abc

Remove abdt_conduitmock and introduce a test suite for conduitmock which
checks the public interface of the mock is identical to the real thing.

Test Plan:
Manually introduce mismatching methods, check they are detected.
$ ./precommit.sh