tests: acknowledge all known failures in declarative autotests

tests: acknowledge all known failures in declarative autotests

This change XFAILs or CONFIG+=insignificant_tests all known failures in
declarative autotests, and links them to bug reports.

Note that the changes were only applied to qpa builds, although it is
possible some of these failures affect other platforms too.

Task-number: QTBUG-20990
Task-number: QTBUG-21000
Task-number: QTBUG-21001
Task-number: QTBUG-21004
Task-number: QTBUG-21005
Task-number: QTBUG-21007
Task-number: QTBUG-21008
Task-number: QTBUG-21009
Task-number: QTBUG-21010
Task-number: QTBUG-21011
Task-number: QTBUG-21012
Task-number: QTBUG-21013
Task-number: QTBUG-21015
Task-number: QTBUG-21016
Task-number: QTBUG-21017
Change-Id: Ieb89aa38e48e9e5162d87483d6441749865f234d
Reviewed-on: http://codereview.qt.nokia.com/3239
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Keith Isdale <keith.isdale@nokia.com>