Investigate if constructor/method maps can be re-used during revalidation

[kjonescertinia]

We have been using a deep hash model to determine if we can re-use constructor/method maps when performing re-validation. This failed when a parameter type was initially unavailable and then became available because the hash only considers the current class source and that of its superclasses/interfaces.

See comment in ApexDeclaration.resetMethodMapIfInvalid() for where the deep hash comparison used to be performed.