JVM_IR: generate $suspendImpl in interfaces as public

The visibility was the cause of KT-44533; not generating `$suspendImpl`
at all makes `super` calls impossible.

^KT-49106 Fixed

compiler/testData/codegen/box/jvm8/defaults/noDefaultImpls/suspendSuperCall.kt

@@ -0,0 +1,34 @@
+// !JVM_DEFAULT_MODE: all
+// TARGET_BACKEND: JVM
+// IGNORE_BACKEND: JVM
+// JVM_TARGET: 1.8
+// WITH_COROUTINES
+// WITH_RUNTIME
+import kotlin.coroutines.*
+import kotlin.coroutines.intrinsics.*
+import helpers.*
+
+suspend fun suspendHere() = suspendCoroutineUninterceptedOrReturn<Unit> {
+    it.resume(Unit)
+    COROUTINE_SUSPENDED
+}
+
+interface MyInterface {
+    suspend fun myMethod(myParam: String): String {
+        suspendHere()
+        return myParam
+    }
+}
+
+class MyImplementation : MyInterface {
+    override suspend fun myMethod(myParam: String): String {
+        suspendHere()
+        return super.myMethod(myParam)
+    }
+}
+
+fun box(): String {
+    var result = "fail"
+    suspend { result = MyImplementation().myMethod("OK") }.startCoroutine(EmptyContinuation)
+    return result
+}