Add dashboard mode support to support testing file dialog

• Add dashboard mode support to pqCoreTestUtility
• Add logic to add/remove file dialog player/translators to support file dialog testing
• Add two file dialog test

Needs: qttesting!69 (merged) and qttesting!70 (merged)

More explanation:

In ParaView, when playing test, a environement variable (DASHBOARD_TEST_FROM_CTEST) is positioned so that some dialog and mechansim are not displayed to shortcut them.

This is very useful but makes it hard to actually test specifically the dialog being shortcutted.

This is now possible thanks to the dashboard mode infrastructure provided by QtTesting.

For standard test, there is no change. The environnement variable will be automatically set when playing/recording tests so that ParaView behave in dashboard mode in that case.

However, when needing to test a shortcut dialog, then the Record test dialog can be used to disable dashboard mode. Then ParaView will behave as if not in dashboard mode.

A dedicated event will be recorded in the XML of the test so that, when playing the test, dashboard mode is also deactivated.

FileDialog player/tranlators are now also only enabled when using dashboard mode.

Developer notes:

• DASHBOARD_TEST_FROM_CTEST is now set when recording tests using Tools->RecordTest.
• Some Qt dialog changes their behavior when DASHBOARD_TEST_FROM_CTEST (already the case before)
• FileDialog QtTesting translator is now only created when DASHBOARD_TEST_FROM_CTEST is set
• QtTesting record dialog now let us disable/enable dashboard mode (QtTesting) and unset/put the DASHBOARD_TEST_FROM_CTEST env var (pqCoreTestUtility)
• When unchecking/checking, an event (dashboard_mode) is recorded in the XML test (handled by QtTesting)
• When playing a test, either through ctest, --play-test or Tools->PlayTest, the DASHBOARD_TEST_FROM_CTEST is set automatically
• When a dashboard_mode event happens, the DASHBOARD_TEST_FROM_CTEST is unset/put, changing behavior of ParaView accordingly