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

analysis/low-level-api-fir/testdata/onAirResolve/replacementInHeader.kt

@@ -0,0 +1,9 @@
+class C<T> {
+    fun x(/*PLACE*/a: Int) {
+
+    }
+}
+
+fun y(/*ONAIR*/b: T) {
+
+}