Move list / dict tests to TestList and TestDict (#22000)
Summary:
There aren't any substantive changes aside from some test renames (e.g. `TestScript.test_dict_membership` -> `TestDict.test_membership`) and the addition of `TestDict.dict()`.
Adding the rest of the dict ops was making the tests a mess and `TestScript` is already > 10000 lines by itself, so breaking them up should make things cleaner
](https://our.intern.facebook.com/intern/diff/15911383/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/22000
Pulled By: driazati
Differential Revision: D15911383
fbshipit-source-id: 614428e03fbc14252f0e9cde74ab9a707169a860
