Issue Type: Bug

Related to #2798.

Suppose I have a line of Python in a space-indented file like this:

    do_something()

I want to wrap it in a conditional, so I add a line above it:

    if condition:
    do_something()

Now I need to indent the body of the conditional, so I click somewhere in the whitespace to the left of that line, and press Tab:

    if condition:
     do_something()

It only inserts one space, awkwardly leaving the line with 5 space indentation when the file is set to use 4 spaces per tab.

Why? Because it only looks at the column position of the cursor when deciding how many spaces to insert, and not the total number of contiguous space characters there are.

This is almost certainly never what a programmer wants.

VS Code version: Code 1.37.1 (f06011a, 2019-08-15T16:16:34.800Z)
OS version: Darwin x64 18.7.0