Prohibit unsupported suspend operators

contains/get/set operators don't work properly on both backends

Also add box test checking that 'compareTo' operator works just fine

 #KT-16219 Fixed

compiler/testData/diagnostics/testsWithStdLib/coroutines/operators.kt

@@ -0,0 +1,28 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+// SKIP_TXT
+
+class A {
+    suspend <!UNSUPPORTED!>operator<!> fun get(x: Int) = 1
+    suspend <!UNSUPPORTED!>operator<!> fun set(x: Int, v: String) {}
+
+    <!UNSUPPORTED!>operator<!> suspend fun contains(y: String): Boolean = true
+}
+
+class B
+suspend <!UNSUPPORTED!>operator<!> fun B.get(x: Int) =1
+suspend <!UNSUPPORTED!>operator<!> fun B.set(x: Int, v: String) {}
+
+<!UNSUPPORTED!>operator<!> suspend fun B.contains(y: String): Boolean = true
+
+class C {
+    suspend fun get(x: Int) = 1
+    suspend fun set(x: Int, v: String) {}
+
+    suspend fun contains(y: String): Boolean = true
+}
+
+class D
+suspend fun D.get(x: Int) =1
+suspend fun D.set(x: Int, v: String) {}
+
+suspend fun D.contains(y: String): Boolean = true