Add value change triggers as methods to handles

[ktbarrett]

I'm not entirely sure why triggers like RisingEdge, FallingEdge, and Edge were made as standalone functions, but since they are parameterizable and only support certain objects, it makes more sense if they are associated only with the objects that support them by making them a method.

await dut.handle.rising_edge()

This will also allow the ability to not have to check the argument type and allow bad behavior.

In lock-step we should deprecate the free-function calls.