Make niceSort a wrapper over niceSortKey id

Currently, niceSort behaves differently than niceSortKey in cases
where the parsed groups are equal but the original not, as it uses
both members of the tuple as opposed to just the first one. Both
niceSortKey and the Python code use only the first one, so in corner
cases we can have different behaviour of these functions.

To rectify this, we change niceSort to be a simple wrapper over
"niceSortKey id", so that we get consistent behaviour.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>