Support for parameter annotations

Adds support for parameter annotations, specifically:

  * Parameter annotations on methods can be inherited/overridden as per the same rules for method annotations.
  * Parameter annotations on methods and constructors can be mixed-in from an unrelated class/interface.

This also refactors the `ResolvedMember` hierarchy to abstract over some common functionality, including the introduction of the `ResolvedParameterizedMember` base class for methods and constructors.

Included is a new test for parameter annotations.