Replace 'allow-disordered-output' with a normalizer that reorders task output groups

[adammurdoch]

"allow-disordered-output" is a very blunt tool to verify the output of a build that does stuff in parallel (which will more and more be the default) and was really only used because the plain console did not group output. Now that it does, a better strategy might be to use a normalizer that reorders task output groups but does not reorder the text within a group.

For example, reorder the groups alphabetically:

Normalize:

> Task :b
some output

> Task :a
other output

To:

> Task :a
other output

> Task :b:
some output