[JVM_IR] Trim the expression test string for null assertions.

^KT-47166 Fixed.

compiler/testData/codegen/box/notNullAssertions/messageLength.kt

@@ -0,0 +1,31 @@
+// TARGET_BACKEND: JVM
+// FILE: test.kt
+
+fun test(): String {
+    return A()
+        // Large comment that would cause the message for
+        // the non-null assertion to be very large if
+        // it is included verbatim in the message.
+        .foo()
+}
+
+fun box(): String {
+    try {
+        test()
+    } catch(e: Throwable) {
+        return if (e.message!!.length <= " must not be null".length + 50) {
+            "OK"
+        } else {
+            "FAIL1"
+        }
+    }
+    return "FAIL2"
+}
+
+// FILE: A.java
+
+public class A {
+    public String foo() {
+        return null;
+    }
+}