Automatically create sort groups based on newlines in organize imports

[MQuy]

Closes#41494.

Based on @RyanCavanaugh's suggestion #41494 (comment)

when organizing imports in each block of newline-contiguous

importcfrom"C";importdfrom"D";importafrom"A";importbfrom"B";

turns into

importcfrom"C";importafrom"A";importbfrom"B";importdfrom"D";

[jakebailey]

This looks about right to me, but I think what I'd like to see are a few more tests to cover cases where there are comments, e.g., what is the behavior when we have something like:

// polyfillimport"lib"// not polyfillimport{b}from"lib2"

or say

import"lib"// xyzimportcfrom"C"

Or similar (this isn't exhaustive). I know the original issue had some code snippets that feature comments.