Add ParameterSource interface.
Add ParameterSourceExpression, which builds up a list of ParameterSource types within the Configuration.
Add ParameterDiscoverer, which produces test method input parameters from any number of sources named in a custom convention.
Phase out deprecated Func-based test method parameter generation in favor of the new ParameterDiscoverer.
Simplify AssertionLibraryFilter construction to better-reflect its actual usage.
Trivial cleanup within ParameterDiscoverer.