feat: replace end2end test and add more test

tests/cond_no_else.test

@@ -0,0 +1,17 @@
+[expected_return_code]
+100
+
+[code]
+fn main() -> i32 {
+    let a = 10;
+    
+    if a == 10 {
+        a = 100;
+    }
+
+    if a == 5 {
+        a = 0; // Should be skipped
+    }
+    
+    return a;
+}