Handle predicates without __name__ in waitForEvent timeouts

[kwy404]

When waitForEvent times out, it builds the error message from predicate.__name__. Callables such as functools.partial objects have no __name__, so instead of CallbackHandlerTimeoutError the caller got an AttributeError. This falls back to the callable's type name (for example partial) in CallbackHandlerBase. The added test with a partial predicate fails before the change and passes after it.

[xpconanfan]

Using repr(predicate) includes memory addresses and bound argument reprs (e.g., <my_module.MyPredicate object at 0x7f...> or functools.partial(<function foo at 0x7f...>, ...)), which makes timeout error messages noisy and harder to match in assertions. Can we fall back to the callable's type name instead?

    predicate_name = getattr(predicate, '__name__', type(predicate).__name__)

(Also, we are removing the deprecated mobly/controllers/android_device_lib/callback_handler.py in a separate PR, so you can drop the changes to callback_handler.py and callback_handler_test.py from this PR.)

[kwy404]

Thanks, good point. Updated to fall back to type(predicate).__name__, and the test now checks that the message names the partial predicate. I also dropped the callback_handler.py change, so the PR only touches CallbackHandlerBase and its test.