Previously, input signals had a bug where when their backing computation or
value would change, it would notify consumers, but consumers would poll the
input signal to check if its value really changed. This polling operation
would transitively poll the input signal's previous dependencies, which of
course would report that they hadn't changed.
This commit adds logic in the `InputSignalImpl` to skip dependency polling
whenever the signal's backing computation or value changes, until that value
is read for the first time.
* splits propertyCreate virtual instructions into DOM vs zone inputs
* integrates with `InputSignal` setting (untested)
* deletes old interfaces/virtual_property impl in favor of Paul's