Set the "is_target" attribute for names, attributes and temps (anything name-like) to preserve that information for later pipeline steps.

Avoid going through an attribute assignment for an intermediate node result since it may not be the end result.

Closes https://github.com/cython/cython/issues/4268

Closes https://github.com/cython/cython/issues/4268

To be used in https://github.com/cython/cython/pull/4241

See https://github.com/cython/cython/pull/3626

Closes https://github.com/cython/cython/issues/4172

Allowing these gives people the false impression that they do something meaningful.

Closes https://github.com/cython/cython/issues/887
Closes https://github.com/cython/cython/issues/3959

People often have unrealistic expectations about what this typing helps with, so I've added a small paragraph to try to make it clearer.

The directives are called `optimize` rather than `optimization`.

1) Entry utility_code wasn't being imported unless the entry was visibly used. The utility code is needed for the definition even if unused. I think this is what utility_code_definition is for, but I'm not completely sure. I also had to add some calls to ensure it's used.

2) CppOptionalTempCoercions weren't being moved correctly. Tested by printing from the destructor.

3) cdef-class attributes weren't being created or destroyed correctly. Tested by printing from the destructor

See https://github.com/cython/cython/issues/4022#issuecomment-870394893

This avoids the need for default constructors of stack allocated variables and temps by allowing late initialisation.

Closes https://github.com/cython/cython/issues/4160

Add missing argument when instantiating a test class. The argument was added in https://github.com/cython/cython/commit/3bd321f17474aafde1bd497163b3e7ba089ee2cc

Fixes https://github.com/cython/cython/issues/4243
(and probably a bunch more annotation bugs)

AnnotationNode doesn't have any child_attrs/subexprs because it mostly doesn't want to be analyzed (it's just transformed to an evaluable string). However this means that InterpretCompilerDirectives wasn't visiting its children to set is_cython_module and so the typing was failing. I've special-cased InterpretCompilerDirectives to visit AnnotationNode fully.

Fixes https://github.com/cython/cython/issues/4198
Fixes https://github.com/cython/cython/issues/4196