Optimize the footprint of the FrameReturnNode

Author: steve-s

graalpython/com.oracle.graal.python.test/testData/goldenFiles/AssignmentTests/annotationType02.tast

@@ -40,4 +40,4 @@ ModuleRootNode Name: <module 'annotationType02'> SourceSection: [0,28]`def fn():
                         IntegerLiteralNode SourceSection: [26,27]`0`
                           Value: 0
                   Return Expresssion: ReadLocalVariableNodeGen SourceSection: None
-                    Frame: [1,<return_val>,Illegal]
+                    Frame: [1,<return_val>,Object]

graalpython/com.oracle.graal.python.test/testData/goldenFiles/AssignmentTests/assignment06.tast

@@ -61,4 +61,4 @@ ModuleRootNode Name: <module 'assignment06'> SourceSection: [0,29]`def fn():↵
                         ReadLocalVariableNodeGen SourceSection: None
                           Frame: [4,<>temp4,Illegal]
                   Return Expresssion: ReadLocalVariableNodeGen SourceSection: None
-                    Frame: [5,<return_val>,Illegal]
+                    Frame: [5,<return_val>,Object]

graalpython/com.oracle.graal.python.test/testData/goldenFiles/AssignmentTests/assignment07.tast

@@ -68,4 +68,4 @@ ModuleRootNode Name: <module 'assignment07'> SourceSection: [0,29]`def fn():↵
                           ReadLocalVariableNodeGen SourceSection: None
                             Frame: [5,<>temp5,Illegal]
                   Return Expresssion: ReadLocalVariableNodeGen SourceSection: None
-                    Frame: [6,<return_val>,Illegal]
+                    Frame: [6,<return_val>,Object]

graalpython/com.oracle.graal.python.test/testData/goldenFiles/AssignmentTests/augassign13.tast

@@ -44,4 +44,4 @@ ModuleRootNode Name: <module 'augassign13'> SourceSection: [0,17]`def fn (): x +
                             Value: 3
                           ObjectLiteralNode SourceSection: None
                   Return Expresssion: ReadLocalVariableNodeGen SourceSection: None
-                    Frame: [1,<return_val>,Illegal]
+                    Frame: [1,<return_val>,Object]

graalpython/com.oracle.graal.python.test/testData/goldenFiles/AssignmentTests/augassign14.tast

@@ -67,4 +67,4 @@ ModuleRootNode Name: <module 'augassign14'> SourceSection: [0,61]`def _method(*a
                           ReadLocalVariableNodeGen SourceSection: None
                             Frame: [5,<>temp5,Illegal]
                   Return Expresssion: ReadLocalVariableNodeGen SourceSection: None
-                    Frame: [6,<return_val>,Illegal]
+                    Frame: [6,<return_val>,Object]

graalpython/com.oracle.graal.python.test/testData/goldenFiles/AwaitAndAsyncTests/asyncFor01.tast

@@ -48,4 +48,4 @@ ModuleRootNode Name: <module 'asyncFor01'> SourceSection: [0,39]`async def f():
                               PythonObjectFactoryNodeGen SourceSection: None
                         BlockNode SourceSection: None
                   Return Expresssion: ReadLocalVariableNodeGen SourceSection: None
-                    Frame: [1,<return_val>,Illegal]
+                    Frame: [1,<return_val>,Object]

graalpython/com.oracle.graal.python.test/testData/goldenFiles/AwaitAndAsyncTests/asyncFor02.tast

@@ -62,4 +62,4 @@ ModuleRootNode Name: <module 'asyncFor02'> SourceSection: [0,42]`async def f():
                               PythonObjectFactoryNodeGen SourceSection: None
                         BlockNode SourceSection: None
                   Return Expresssion: ReadLocalVariableNodeGen SourceSection: None
-                    Frame: [4,<return_val>,Illegal]
+                    Frame: [4,<return_val>,Object]

graalpython/com.oracle.graal.python.test/testData/goldenFiles/AwaitAndAsyncTests/asyncWith01.tast

@@ -46,4 +46,4 @@ ModuleRootNode Name: <module 'asyncWith01'> SourceSection: [0,34]`async def f():
                         YesNodeGen SourceSection: None
                         GetClassNodeGen SourceSection: None
                   Return Expresssion: ReadLocalVariableNodeGen SourceSection: None
-                    Frame: [0,<return_val>,Illegal]
+                    Frame: [0,<return_val>,Object]

graalpython/com.oracle.graal.python.test/testData/goldenFiles/AwaitAndAsyncTests/asyncWith02.tast

@@ -63,4 +63,4 @@ ModuleRootNode Name: <module 'asyncWith02'> SourceSection: [0,47]`async def f():
                         YesNodeGen SourceSection: None
                         GetClassNodeGen SourceSection: None
                   Return Expresssion: ReadLocalVariableNodeGen SourceSection: None
-                    Frame: [2,<return_val>,Illegal]
+                    Frame: [2,<return_val>,Object]

graalpython/com.oracle.graal.python.test/testData/goldenFiles/AwaitAndAsyncTests/await01.tast

@@ -41,4 +41,4 @@ ModuleRootNode Name: <module 'await01'> SourceSection: [0,28]`async def f():↵
                             Identifier: smth
                             ReadAttributeFromObjectNotTypeNodeGen SourceSection: None
                   Return Expresssion: ReadLocalVariableNodeGen SourceSection: None
-                    Frame: [0,<return_val>,Illegal]
+                    Frame: [0,<return_val>,Object]