Prepare roottest for ROOT 7's ownership model

[hageboeck]

In essence, add histo.SetDirectory(xxx) to all places where a histogram should show up in a TDirectory independent of whether it has been registered automatically.

[github-actions]

Test Results

    22 files      22 suites   3d 3h 45m 55s ⏱️
 3 800 tests  3 797 ✅ 1 💤 2 ❌
75 511 runs  75 500 ✅ 9 💤 2 ❌

For more details on these failures, see this check.

Results for commit 38b6fdd.

♻️ This comment has been updated with latest results.

[pcanal]

We should enhanced this PR by adding a new test that checks the current memory ownership explicitly (Otherwise we no longer test the current/main-stream usages)

[hageboeck]

We should enhanced this PR by adding a new test that checks the current memory ownership explicitly (Otherwise we no longer test the current/main-stream usages)

That's a very good idea, and it's now implemented in the "master" PR for this feature. I'll cherry-pick the commit that will work already in ROOT 6 mode into this PR next.

Edit: Done

[pcanal]

Thanks.

[hageboeck]

Only the known failures, merging ...