PY3 generator types and names minor update
PY3 generator types and names minor update

Summary:
Minor update:
1) generate_types_array() removed
2) minor types (excplicit auto* vs just auto, and constness added where possible) and naming updates

Reviewed By: junzh0u, Filip-F

Differential Revision: D39138408

fbshipit-source-id: 60a4aa5d1327b280e9490a6aceeffa35c07da5b9

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