Remove the use of iterators from NodeTraversal.getAbstractScope.
Remove the use of iterators from NodeTraversal.getAbstractScope.

This iterator alone accounted for ~3% of GC garbage in a sample profile.

PiperOrigin-RevId: 469470995

ChadKillingsworth/closure-compiler,monetate/closure-compiler,monetate/closure-compiler,google/closure-compiler,monetate/closure-compiler,google/closure-compiler,ChadKillingsworth/closure-compiler,google/closure-compiler,monetate/closure-compiler,google/closure-compiler,ChadKillingsworth/closure-compiler,ChadKillingsworth/closure-compiler