Use proper type for context 'this'

Bug in 'generateThisOrOuterFromContext', it worked while instance of a
class was always an object.

 #KT-27078

compiler/testData/codegen/box/inlineClasses/contextsAndAccessors/captureInlineClassInstanceInLambda.kt

@@ -0,0 +1,10 @@
+// !LANGUAGE: +InlineClasses
+// IGNORE_BACKEND: JVM_IR
+
+inline class R(private val r: Int) {
+    fun test() = { ok() }()
+
+    fun ok() = "OK"
+}
+
+fun box() = R(0).test()

compiler/testData/codegen/box/inlineClasses/contextsAndAccessors/captureInlineClassInstanceInObject.kt

@@ -0,0 +1,12 @@
+// !LANGUAGE: +InlineClasses
+// IGNORE_BACKEND: JVM_IR
+
+inline class R(private val r: Int) {
+    fun test() = object {
+        override fun toString() = ok()
+    }.toString()
+
+    fun ok() = "OK"
+}
+
+fun box() = R(0).test()