Kapt+JVM_IR: do not require KtFile for each generated class

In particular, JVM IR doesn't provide KtFile for a multifile facade in
JvmDeclarationOrigin (JVM backend provides KtFile of a random multifile
part). This led to multifile classes being completely ignored in the
JVM_IR version of kapt. Now they are generated correctly and the changed
test passes, but there's a _ir.txt expectation file because the order of
'foo' and 'bar' is different (which is not a problem).

plugins/kapt3/kapt3-compiler/testData/converter/multifileClass.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 // WITH_STDLIB
 
 // FILE: a.kt

plugins/kapt3/kapt3-compiler/testData/converter/multifileClass_ir.txt

@@ -0,0 +1,30 @@
+package test;
+
+@kotlin.Metadata()
+public final class M1 {
+
+    public M1() {
+        super();
+    }
+
+    public static final void bar() {
+    }
+
+    public static final void foo() {
+    }
+}
+
+////////////////////
+
+package test;
+
+@kotlin.Metadata()
+public final class M2 {
+
+    public M2() {
+        super();
+    }
+
+    public static final void baz() {
+    }
+}