Implement NoReduntantLambdaFunction

[isidentical]

I am not sure whether this tool itself accepts new rules or not, I just wanted to play with it a little bit so drafted a PR, if the built-in ruleset is intended to kept only for 'selected' rules, it is OK to close this PR.

Summary

• Implements a lint rule for 'redundant lambda wrapping'.
  The pattern mostly happens on function compositions, like Pool.execute(<func>) or even map.

def square(x):
    return x ** 2
map(lambda x: square(x), [1,2,3,4])

becomes

def square(x):
    return x ** 2
map(square, [1,2,3,4])

Test Plan

I've added both valid and invalid test cases, not sure if more are needed.

[jimmylai]

@isidentical new rules are definite welcome, especially those generic rules that can make code cleaner, safer or more efficient.

[jimmylai]

Thanks for contributing! This is a very useful autofixer which can make the code simpler and more efficient!
I was able to easily find hundreds of violations in our codebase.
Just some minor change requests.

[jimmylai]

Looks awesome!

[isidentical]

Looks awesome!

Wow, Thanks! (You are so fast!)