Replace node.walk(Reference) with node.reference_acesses()

[sergisiso]

Oncee #2527, #2424, #2271 are fixed, we need to replace many: for node in expr.walk(Reference) with the reference_accesses version because it currently misses all references that are not nodes in a tree (e.g. kinds) and it currently needs awkward ancestor checks (e.g. if (isinstance(ref.parent, Call) and ref is ref.parent.children[0])) to see if it was a data symbol or some call or type symbol, which often we don't need.