graphing/designer: test the query filters through their real widgets

The stub hid the input's mount-time report, so the tests asserted a context
shape the form never produces. The filter definitions the tests describe move
to the shared fixtures, the app test included.

Change-Id: Ibff72a444573804dd45970d56d50e72d0f1d35f2
JIRA-Ref: CMK-38111