[SLC] AbstractSymbolLightClassesByPsiTest: add more stable order

Now more diff between sources and libraries are readable.
Also prefer .descriptors to .fir as FIR is a first-class support

^KT-62892

compiler/testData/asJava/lightClasses/lightClassByPsi/scripts/InnerClasses.descriptors.java

@@ -0,0 +1,29 @@
+public static final class Bar /* InnerClasses.Bar*/ {
+  private final int a;
+
+  private final int b;
+
+  public  Bar(int);//  .ctor(int)
+
+  public final int getA();//  getA()
+
+  public final int getAPlusB();//  getAPlusB()
+
+  public final int getB();//  getB()
+
+  class Baz ...
+}
+
+public static final class Baz /* InnerClasses.Bar.Baz*/ {
+  public  Baz();//  .ctor()
+
+  public final void doSomething();//  doSomething()
+}
+
+public final class InnerClasses /* InnerClasses*/ extends kotlin.script.templates.standard.ScriptTemplateWithArgs {
+  public  InnerClasses(java.lang.String[]);//  .ctor(java.lang.String[])
+
+  public static final void main(java.lang.String[]);//  main(java.lang.String[])
+
+  class Bar ...
+}