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

"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
```

Start by locating the handling of "allow-disordered-output" and the code that captures or verifies task output groups. Compare that behavior with the plain console's grouping, then define how groups should be reordered while preserving text within each group. Done means the normalizer handles the example and existing verification behavior remains correct.

Written by the indexing model from the issue text.