BoxIO : Fix noduleLayout:section from opposite direction source plugs

[murraystevenson]

noduleLayout:section metadata copied from the source plug is only valid when the source plug and the BoxIO's promoted plug are of the same direction. A BoxIn set up from an out plug with noduleLayout:section "bottom" registered would cause its promoted in plug to also appear on the bottom of the Box. This is common with EditScopes as they set up both their BoxIn and BoxOut from the same source plug.

We now choose the target of setupNoduleSectionMetadata() based on the direction of the source plug, rather than m_direction. When they match, the existing behaviour is unchanged. When they don't match, the metadata target is now the promoted plug, overwriting any noduleLayout:section metadata copied from the source.

An alternate approach might be to always call setupNoduleSectionMetadata() for both outPlugInternal() and inPlugInternal(), I think that might help ensure the internal plugs better represent the flow of their external equivalents in cases where an EditScope is set up with an in plug on the left and the out on the right (note the current lack of "noduleLayout:section" metadata on the internal BoxIO plugs in the additions to BoxInTest/BoxOutTest). But in the general case that feels like it'd only further proliferate instance noduleLayout:section metadata registrations unless we only registered instance metadata when it differs from the default...