Refine types

[charmoniumQ]

Resolves #2.

This pull request is the result of:

• Merging @NeilGirdhar's types in Add type annotations for Graph and DiGraph networkx/networkx#4014 (classes/graph.pyi and classes/digraph.pyi).
• Adding my own (classes/reportviews.pyi, classes/coreviews.pyi).
• Fixing all of the problems uncovered by mypy 0.971.
  • form .blah import * pulls in whatever type variables you have, and if there are two of the same name, Mypy complains. Therefore, I prefixed all of the type variables with an underscore, so they don't get pulled in by *.
  • If mypy flagged an annotation that is internal to NetworkX, I deleted that annotation rather than fix it. I decided something is internal if it had a leading underscore, or in some cases, if it wasn't documented by NetworkX.
  • Removing test code in NetworkX.
  • Unfortunately type variables can't themselves take type parameters, so this doesn't work:

    T = TypeVar("T")
    GT = TypeVar("GT", bound=Graph)
    graph: GT[T]
    
    In such cases, I converted graph to Any, as it is elsewhere in the stubs.

I will add automated tests in a future PR.