When an actual appmap doesn't match the expected one, show it as JSON to
make it easier to understand why they're different (and to assist with
updating the expected, if appropriate).

With the previous function in simple.py, the return event generated to
check that numpy.int64 serialized correctly didn't test AppMapEncoder.
Keys in a dict that are in a return event are rendered with "repr"
before the event gets serialized. "repr(int64(0))" returned "0" in 1.x,
but returns "numpy.int64(0)" in 2.x, which caused the test to fail.

Fix tests that fail with numpy v2

Any class function decorated with @Property, or any class attribute with
a property as a value, will now be instrumented.

feat: instrument properties

# [2.1.0](v2.0.10...v2.1.0) (2024-07-03)

### Features

* instrument properties ([d69b6e1](d69b6e1))