[359244] Provide API to get all locked objects

Add InternalLockManager.getLockStates() method in API to be able to get
all locked objects.

Bug: 359244
Change-Id: I76546c05c01f062c265255745c46fe276b536d4c
Signed-off-by: Esteban Dugueperoux <esteban.dugueperoux@obeo.fr>
[449665] IllegalArgumentException on CDOResource.cdoLockState()

IllegalArgumentException is thrown when calling
CDOResource.cdoLockState() in Adapter notification when calling
transaction.getResource(); because the CDOResource is in CDOState.PROXY
before CDOResource.load() is called.

Change-Id: Ia7f0cf2619857f7d787df28cdaa8ae368e8bbe28
Task-Url: https://bugs.eclipse.org/bugs/show_bug.cgi?id=449665
Signed-off-by: Esteban Dugueperoux <esteban.dugueperoux@obeo.fr>