[FIR] Add tests for K2-only suspend operators get/set/contains

#KT-57169

compiler/testData/codegen/box/operatorConventions/suspendOperators.kt

@@ -0,0 +1,34 @@
+// WITH_STDLIB
+// WITH_COROUTINES
+// IGNORE_BACKEND_K1: ANY
+// IGNORE_BACKEND: WASM
+
+import kotlin.coroutines.*
+import kotlin.coroutines.intrinsics.*
+
+fun <T> runBlocking(c: suspend () -> T): T {
+    var res: T? = null
+    c.startCoroutine(Continuation(EmptyCoroutineContext) {
+        res = it.getOrThrow()
+    })
+    return res!!
+}
+
+class A {
+    var value = ""
+
+    suspend operator fun get(x: Int) = value
+    suspend operator fun set(x: Int, v: String) {
+        value = v
+    }
+
+    operator suspend fun contains(y: String): Boolean = y == value
+}
+
+fun box() = runBlocking {
+    val a = A()
+    if ("" !in a) return@runBlocking "FAIL"
+    a[1] = "OK"
+
+    a[2]
+}