FIR IDE: move low level api testdata sources to the analysis directory

analysis/low-level-api-fir/testdata/fileStructure/enumClass.kt

@@ -0,0 +1,13 @@
+enum class A {/* NonReanalyzableDeclarationStructureElement */
+    X,
+    Y,
+    Z
+
+    ;
+
+    fun foo(){/* ReanalyzableFunctionStructureElement */}
+
+    val x = 10/* NonReanalyzableDeclarationStructureElement */
+
+    fun bar() = 10/* NonReanalyzableDeclarationStructureElement */
+}