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/outerThisInInnerInitBlock.kt

@@ -0,0 +1,19 @@
+class Outer {
+    inner class Inner {
+        init {
+            class NamedLocal {
+                fun foo() {
+                    outer()
+                }
+            }
+        }
+    }
+
+    fun outer() {}
+}
+
+// JVM_TEMPLATES
+// 1 final synthetic LOuter\$Inner; this\$0
+
+// JVM_IR_TEMPLATES
+// 1 private final synthetic LOuter; this\$0