Use `FilterChainInterface` and `ValidatorChainInterface` in type declarations

[adambalint-srg]

Feature Request

Q	A
New Feature	yes
RFC	no
BC Break	no

Summary

As noted in laminas/laminas-validator#429 final classes should use interfaces. Because instead of extending this class the only option to modify these functionalities is to decorate the class. But in this repository the ValidatorChain and FilterChain classes are used in type declaration, so I can't use my custom classes for this. FilterChain already has an interface, for ValidatorChain I've created a PR: laminas/laminas-validator#430, so I hope it will be approved soon.

I know the new release is under construction, so this is a request to include these changes to ne new release

[gsteel]

Note, neither FilterChainInterface nor ValidatorChainInterface were made iterable or Countable and now it's too late. Additionally, there is no interface method for getValidators(), which is problematic when preparing an error message for empty inputs.

Inspecting/manipulating the chain inside input-filter is a bad idea anyway and generating error messages outside of validators internals prevents translation amongst other problems…