Now that all cells are modeled as `NewCellVariable` in Dynamo, we no
longer need to put cell variables into this special `closure_cells`,
rather we just merge `closure_cells` with `symbolic_locals`.
This allows us to merge and remove some code paths, notably make
`LOAD_CLOSURE` the same as `LOAD_FAST`, and `LOAD_DEREF` & `STORE_DEREF`
the same for inlining or regular `InstructionTranslator`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/140154
Approved by: https://github.com/jansel
ghstack dependencies: #140330, #140152, #140436, #140435, #140153
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