Use FunctionTypedElement.type while generating method overrides
Turns out FunctionTypedElement.typeParameters could be inconsistent
for MethodMembers returned by InheritanceManager3.getMember2.
FunctionTypedElement.type.typeFormals seem to be always good, but
we have to also use type.parameters and type.returnType instead
of just parameters and returnType in this case.
Use
FunctionTypedElement.typewhile generating method overridesTurns out
FunctionTypedElement.typeParameterscould be inconsistent forMethodMembers returned byInheritanceManager3.getMember2.FunctionTypedElement.type.typeFormalsseem to be always good, but we have to also usetype.parametersandtype.returnTypeinstead of justparametersandreturnTypein this case.Fixes https://github.com/dart-lang/mockito/issues/658