Use DataHandles in AthenaOutpuStreamTool

Merged Tomasz Bold requested to merge tbold/athena:outputTool-to-dh into master

This MR is to fix ATLASRECTS-4684. It is rather clear that a complete replacement of raw SG access is not quite possible in this particular tool some aspects can be. One of them is AthenaAttrList access.

This needs approval from @gemmeren and/or @mnowak

Edited by Tomasz Bold

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