[FIR-TEST] Move analysis tests to separate module

compiler/fir/analysis-tests/testData/resolve/cfg/emptyWhen.kt

@@ -0,0 +1,12 @@
+// !DUMP_CFG
+fun test_1() {
+    when {}
+}
+
+fun test_2(x: Int) {
+    when (x) {}
+}
+
+fun test_3(x: Int) {
+    when (val y = x) {}
+}