DOC: organize stringmethods in what's new
Added summarized section to the release note based on the discussion in  #9386

@sinhrks Thanks! But, you will have to rebase (and probably solve some conflicts after my PR that reorganized the whatsnew file a bit). But you can put the section under "New features" (eg just before 'other enhancements')
 Sure, rebased.
 @sinhrks Merged this, thanks! I will look into the docstring linking thing. Ping #9599
