Check for AssignmentExpr uses

[fabsx00]

Some AST nodes (AssignmentExpr in particular) have been renamed during the development of the php support for joern (see octopus-platform/joern#86). Before we merge the php-support, we need to ensure that none of the steps rely on old node names.

[malteskoruppa]

Additionally, UnaryOp was renamed into UnaryOperationExpression, see octopus-platform/joern#88.

[malteskoruppa]

Similarly, IncDecOp was renamed into PostIncDecOperationExpression, see octopus-platform/joern#89.