[470599] Do not check for uniqueness while installing xRefAdapter

Port of the patch "Reducing algorithmic complexity of the
ECrossReferenceAdapter" proposed in EMF Core :

https://git.eclipse.org/r/#/c/54826/1

Bug: 470599
Change-Id: I53a2d263c374b93d3d45db897fbe1b17bdeccfc1
Signed-off-by: Cedric Brun <cedric.brun@obeo.fr>
3 files changed