[BC BREAK] Introduce new ClassJoinpoint->getScope() API

[lisachenko]

This PR introduces a new API for working with scope and instances. Previously, all joinpoints have had the getThis() method which was strange for FunctionInvocation as it couldn't have a reference to the object. Thus, new ClassJoinpoint interface was added to provide explicit information about class joinpoints via getScope(), getThis() and isDynamic() methods.

Notable changes:

• Removed the Joinpoint->getThis() method, as not all joinpoints belong to classes (eg. FunctionInvocation)
• Introduce the new ClassJoinpoint interface with getScope(), getThis() and isDynamic() methods
• Removed the Joinpoint->getStaticPart() method as it can return anything, better to use explicit methods.

[scrutinizer-notifier]

The inspection completed: 16 updated code elements