JVM_IR: keep nullability when remapping type parameters

compiler/testData/codegen/box/javaInterop/notNullAssertions/nonNullableTypeParameter.kt

@@ -0,0 +1,22 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// TARGET_BACKEND: JVM
+// FILE: a.kt
+interface I {
+    fun <T : String> f(x: T) = x
+}
+
+class C : I
+
+fun box() = try {
+    B.f()
+    "FAIL"
+} catch (e: IllegalArgumentException) {
+    "OK"
+}
+
+// FILE: B.java
+public class B {
+    public static String f() {
+        return new C().<String>f(null);
+    }
+}

compiler/testData/codegen/box/javaInterop/notNullAssertions/nullableTypeParameter.kt

@@ -0,0 +1,9 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// TARGET_BACKEND: JVM
+interface I {
+    fun <T : String> f(x: T?) = x ?: "OK"
+}
+
+class C : I
+
+fun box() = C().f<String>(null)