[440032] DRAFT - Rework DiagramMappingsManager and co

Introduce DiagramMappingManagerKey

DiagramMappingManager now has to be retrieved for each refresh.
NoLayer mode is extracted in its own class.

Cleanup and eviction strategy is now less prone to errors

Do not use listener and dispose logic which makes no sense anymore

Change-Id: I3f350a37fd0102641b0c6e93391ea7c19f1b58c0