outcome results index api

fixes CNVS-10898

test plan
- fetch outcome results using the new endpoint
- ensure that outcome results are returned
- fetch outcome results with include[]="alignments"
- ensure that alignments are included

filtering and including is largely identical to the result rollup
endpoint. may want to exercise some of those that make sense, too.
e.g. filtering by user_ids makes sense and should work. including
courses or an aggregate parameter doesn't make sense, so we don't
care if it doesn't work

Change-Id: Ifd1540304cc5e0f98d3c2e6121a3d984b8b662b5
Reviewed-on: https://gerrit.instructure.com/30451
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>
Reviewed-by: Jon Willesen <jonw@instructure.com>
Product-Review: Joel Hough <joel@instructure.com>