WELD-1791 Revisit configuration

- introduce WeldConfiguration per-deployment service
- supported configuration keys can be found in ConfigurationKey enum
WELD-1791 Make findbugs happy
WELD-1787 Preparation work
WELD-1787 Cache resolved observers within EventImpl
WELD-1787 Cache EventMetadata within EventImpl
WELD-1787 Make code more reusable
WELD-1787 Make it possible for a TypeSafeResolver to return a different type after finalizing
WELD-1787 Cache ResolvedObservers
WELD-1787 Get rid of EventPacket
WELD-1787 Cache whether event metadata is required by any of the observers
WELD-1787 Minor
WELD-1787 Resolvables - remove unused methods
WELD-1787 Resolvables - more cleanup
WELD-1787 Resolvables - addQualifierUnchecked
WELD-1787 Resolvables - simplify ResolvableBuilder