Add required-users to DV2 manual results.

Filter out manual results when finding "final" DV2 results now that
they are also associated with the build from which they're derived.
Add required-users support to DV2 Filters that request other results.
Add required-users to remaining DV2 Filter tests.
Add required-users support to CopyCat and its DV2 component.

CHANGELOG: `gmt copy-cat somatic` now takes the ID of the saved
annotation data directly instead of a reference ID and version.
Add required-users to DV2 Detector tests.