[FE] Support local contextual declarations

compiler/testData/diagnostics/tests/extensions/contextReceivers/localDeclaration.kt

@@ -0,0 +1,28 @@
+interface A {
+    fun f() {}
+}
+class B : A
+
+fun testLocalFunction() {
+    context(A)
+    fun local() {
+        f()
+    }
+    with(B()) {
+        local()
+    }
+    <!NO_CONTEXT_RECEIVER!>local()<!>
+}
+
+fun testLocalClass() {
+    context(A)
+    class Local {
+        fun local() {
+            f()
+        }
+    }
+    with(B()) {
+        Local().local()
+    }
+    <!NO_CONTEXT_RECEIVER!>Local()<!>
+}