Add automated test for "Display Left Panel Column from Administer Wiki"

The manual test is here: https://test.xwiki.org/xwiki/bin/view/Administration%20Tests/Display%20Left%20Panel%20Column

The test verifies that the panels from the left column are displayed properly when changed from Wiki Administration.

Matrix discussion: https://matrix.to/#/!ikPtGZaGWtyblizzlR:matrix.xwiki.com/$16481282921086aAjRB:matrix.xwiki.com?via=matrix.org&via=matrix.xwiki.com&via=caubin.fr

Vincent Massol: The test verifies that the right panels can be changed from the UI
See https://github.com/xwiki/xwiki-platform/blob/0f310b86c6cefca1883a367ca873d1455374ae02/xwiki-platform-core/xwiki-platform-panels/xwiki-platform-panels-test/xwiki-platform-panels-test-docker/src/test/it/org/xwiki/panels/test/ui/docker/PanelIT.java#L149

but there's no test for the left panels
Also it tests the ability to set one 1 panel, the test could be improved to set more than 1 panel, separated by commas

Ilie Andriuta: I see, thanks!
I will create a task for the left panels, and will modify the manual test for right panel to display more than 1 panel

Vincent Massol:
Ilie Andriuta: you could also note that we have an indirect test for using a comma-separated list at https://github.com/xwiki/xwiki-platform/blob/4f0ce2e80067a361f9822e1c8ef690cd9e593b8b/xwiki-platform-core/xwiki-platform-menu/xwiki-platform-menu-test/xwiki-platform-menu-test-docker/src/test/it/org/xwiki/menu/test/ui/MenuIT.java#L108
(this adds a new menu as a panel using the left panels)

 Ilie Andriuta: Vincent Massol: ok, so the automated tests check the same things as the manual ones after all, so no task should be created after all
I will update the manual test with the necessary details.

Vincent Massol: not exactly
for the left panels, the admin ui is not tested

Ilie Andriuta: ah, ok, so I will create a task for Left Panel to be safe

Vincent Massol: better have a direct one inside PanelIT
it's easy to add