Improve Python statement range provider

[juliasilge]

We've gotten some helpful feedback on the Python statement range provider outlining some improvements.

Consider this function, where you have x defined locally so you can step through the function:

def add_some_numbers(x):
    y = x + 1
    z = (y > 4 &
    True)
    z

1. Put your cursor at the end of line 2. Only that line is identified and Cmd+Enter works well but it moves the cursor forward to the end of the function, still inside but at the end.
2. Put your cursor at the end of line 3. The whole function is identified as the statement, which is surprising.
3. Select more than one line with your mouse, such as starting at y and ending at True) then send via Cmd+Enter. Because of the whitespace, the execution errors. This one may be the hardest to make feel nice because of Python whitespace issues.