Close Find/Replace test's Welcome page without leaving it maximized

[HeikoKlare]

FindReplaceOverlayInEditorTest opens an editor and expects the Find/Replace overlay placed on it to take the focus. In a full product on a fresh workspace, the workbench shows its Welcome page first, which the test closes beforehand. That page is shown maximized, so closing it leaves the window maximized on a part that is gone. An editor opened afterwards is never rendered into the window but remains in the rendering engine's limbo, where it is invisible, and nothing inside an invisible widget tree can take the focus. The overlay therefore never received it, and the first test of the class failed.

This only happens where a Welcome page exists at all, which is the Ant-based test execution in the full SDK, and neither in the IDE nor via Maven Tycho. Putting the page into standby restores the window's regular layout before the page is closed, which makes the editor render as expected. Since the page does not come back afterwards, closing it once per class instead of before every test is sufficient.

The message reported when the focus is missed now also names the control holding it instead, so that a comparable failure can be told apart from an inactive window or a competing focus request without having to reproduce it first.

To find this, the Jenkins setup was rebuilt locally: the SDK and the automated tests of the failing I-build were installed the way the Ant harness does, and the suite was run through org.eclipse.test.uitestapplication with a fresh workspace, so that the Welcome page is present. The failure reproduced in all 9 runs of the unchanged build and disappeared in all runs with this change.

Fixes #4349

[github-actions]

Test Results

   858 files  ±0     858 suites  ±0   56m 48s ⏱️ - 1m 1s
 8 280 tests ±0   8 037 ✅ ±0  243 💤 ±0  0 ❌ ±0 
20 709 runs  ±0  20 039 ✅ ±0  670 💤 ±0  0 ❌ ±0 

Results for commit 9ba4b22. ± Comparison against base commit b994f34.