Lot of compiler code uses HashMap or HashSet and iterates over them. The
iterator returned by HashMap/ HashSet is known to be unstable in
traversal order.

Change-Id: I676596fa3e427f07ba6089d8d93346b5b5d9200c
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>
Reviewed-on: https://git.eclipse.org/r/c/jdt/eclipse.jdt.core/+/189993
Tested-by: JDT Bot <jdt-bot@eclipse.org>