PEX: Inconsistent error/return values depending on which requirements aren't met

PresentationDefinition.Match() returns:

• no error and no VCs when InputDescriptor constraints aren't met
• an error when submission requirements aren't met (e.g.: Presentation Definition with 2 InputDescriptors, 1 for JSON-LD, 1 for JWT, pick 1)

Both situations are functionally valid flows, and should not yield a (hard) error. But the caller might still want to have details on what failed to match (e.g. format). Maybe we should return a special error type for matching failures (not errors, e.g. invalid definition), which can be tested with errors.As (or Is), which also contains detailed information?

Start with PresentationDefinition.Match() and compare its behavior when InputDescriptor constraints fail with behavior when submission requirements fail. Done should mean both valid non-matches avoid a hard error while still exposing enough failure detail for callers to inspect.