Implement script instance capturing in script lowering

for regular classes only. Reimplementing the main behavior of the
old BE and implementing few cases on top of it.
#KT-19423 fixed

compiler/testData/codegen/script/scriptInstanceCapturing/classCapturesProperty.kts

@@ -0,0 +1,11 @@
+// IGNORE_BACKEND: JS, JS_IR, JS_IR_ES6, NATIVE, WASM
+
+// expected: rv: abc
+
+// KT-19423
+val used = "abc"
+class User {
+    val property = used // error: Expression is inaccessible from a nested class
+}
+
+val rv = User().property