Revert the search depth behavior changes from #154

This reverts parts of the changes from #154: Before merging the pull
request, a depth of 1 returned just the pages in the root namespace.
With the

Revert the search depth behavior changes from #154

This reverts parts of the changes from #154: Before merging the pull
request, a depth of 1 returned just the pages in the root namespace.
With the changes in the pull request, a depth of 1 also returned pages
in subnamespaces of the root namespace (as it was also tested in the test case).
This reverts this part of the changes and a depth of 1 returns just the
pages in the root namespace again.

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fixed test case

Added test for search_allpages

Currently both the 2nd and the third assertions fail
(the first one is just for upcoming non-regression)

removed unecessary requiresin unit tests

moved _testing to _test