PY-42693 (wip): Infer completitions for lambda parameters in PyCharm

[Christopher-Chianelli]

A partial fix for https://youtrack.jetbrains.com/issue/PY-42693/PyCharm-cannot-infer-type-for-lambda-parameters

Added a new TypeProvider that tries to determine the callable type of a lambda in Python. In particular:

• If the lambda is part of an argument list that has a call expression with a known callee
• Then it finds the position of the lambda inside the argument list, and resolves the callee. The type of the entire lambda expression is determined to be the same as the type of the Nth argument of the callee (where N is the lambda's position in the argument list).

Modified PyTypingTypeProvider to determine type of lambda named parameters. In particular:

• If a NamedParameter is in a parameter list belonging to a lambda expression
• Then get the type of the Nth parameter (where N is the index of the NamedParameter in the lambda expression)

With these changes, code completions work; i.e., given

from typing import Callable

class A:
    my_attribute: int

def function(a: A, fun: Callable[[A], int]):
    return fun(a)

a = A()
a.my_attribute = 10
function(a, lambda parameter: parameter.my_

it would suggest the completion "my_attribute", which has type "int".

However, code insights still suggests parameter is Any, and doesn't seem to check the return type of the lambda expression.

Needs tests.

(I am unfamiliar with the code base and unsure where to go from here)