Add automated test for "See The Logging Page"

Note that we already have a PageTest at https://github.com/xwiki/xwiki-platform/blob/848287c4ab19b06af87280c3fe0d18004fd773a2/xwiki-platform-core/xwiki-platform-logging/xwiki-platform-logging-ui/src/test/java/org/xwiki/logging/LoggingAdminPageTest.java#L74 that is covering set-level, unset-level, and the unknown-logger error path at the rendering level (mocked LoggerManager).

There's also https://github.com/xwiki/xwiki-platform/blob/53ce83181a6e2ec2a97587190c1b6948c1bc6b6c/xwiki-platform-core/xwiki-platform-logging/xwiki-platform-logging-script/src/test/java/org/xwiki/logging/script/LoggingScriptServiceTest.java that unit-tests the logging script service + PROGRAM-right check.

What we are strictly missing:

• Steps 1 and 2 of the manual test (ie that the Logging section exists and can be clicked in the admin UI)
• That the Action button works to set a logging level (the setting itself works and is tested in the page test)

Now if we implement the missing checks, then the page test becomes almost irrelevant (except for the unknown logger part)...