JVM_IR: KT-40330 Unify field names for captured 'this' with JVM

NB some cases such as captured extension receiver for an extension
lambda are not supported yet; to be discussed, to what extent should we
actually follow JVM code shape here.

compiler/testData/codegen/bytecodeText/fieldsForCapturedValues/extensionLambdaExtensionReceiver.kt

@@ -0,0 +1,22 @@
+class Receiver {
+    fun foo() {}
+}
+
+fun useExtensionLambda(lambda: Receiver.() -> Unit) {
+}
+
+fun test() {
+    useExtensionLambda { 
+        class NamedLocal {
+            fun run() {
+                foo()
+            }
+        }
+    }
+}
+
+// JVM_TEMPLATES
+// 1 final synthetic LReceiver; \$this_useExtensionLambda
+
+// JVM_IR_TEMPLATES
+// 1 private final synthetic LReceiver; \$this