[region-isolation] Look through actor isolated, non-Sendable struct_element_addr geps.

Just an initial commit. Going to add more tests.

rdar://127006035.

Author: gottesmm

lib/SILOptimizer/Analysis/RegionAnalysis.cpp

@@ -188,17 +188,6 @@ struct UseDefChainVisitor
       case ProjectionKind::Struct:
         auto *sea = cast<StructElementAddrInst>(inst);
 
-        // See if our type is actor isolated.
-        if (!bool(actorIsolation)) {
-          auto i = getActorIsolation(sea->getStructDecl());
-          // If our parent type is actor isolated then we do not want to keep on
-          // walking up from use->def since the value is considered Sendable.
-          if (i.isActorIsolated()) {
-            actorIsolation = i;
-            return SILValue();
-          }
-        }
-
         // See if our result type is a sendable type. In such a case, we do not
         // want to look through the struct_element_addr since we do not want to
         // identify the sendable type with the non-sendable operand. These we