Diff should typehint DateFormatter interface rather than a specific implementation

Problem/Motivation

Various classes typehint the injected date.formatter service with the default implementation rather than the interface.This leads to problem like when modules try to decorate or override the service.

Steps to reproduce

Decorate or replace date.formatter with a different class.

Proposed resolution

Typehint constructor with interface, not concrete implementation.

User interface changes

Nil

API changes

Nil

Data model changes

Nil