[test] Add failing test showing useMemo bug

compiler/forget/src/__tests__/fixtures/compiler/useMemo-inlining-block-return.expect.md

@@ -0,0 +1,46 @@
+
+## Input
+
+```javascript
+// @inlineUseMemo
+function component(a, b) {
+  let x = useMemo(() => {
+    if (a) {
+      return { b };
+    }
+  }, [a, b]);
+  return x;
+}
+
+```
+
+## Code
+
+```javascript
+// @inlineUseMemo
+function component(a, b) {
+  const $ = React.unstable_useMemoCache(3);
+  if (a) {
+    const c_0 = $[0] !== b;
+    let t0;
+    if (c_0) {
+      t0 = { b };
+      $[0] = b;
+      $[1] = t0;
+    } else {
+      t0 = $[1];
+    }
+    let t1;
+    if ($[2] === Symbol.for("react.memo_cache_sentinel")) {
+      t1 = t0;
+      $[2] = t1;
+    } else {
+      t1 = $[2];
+    }
+  }
+  const x = t1;
+  return x;
+}
+
+```
+      

compiler/forget/src/__tests__/fixtures/compiler/useMemo-inlining-block-return.js

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+// @inlineUseMemo
+function component(a, b) {
+  let x = useMemo(() => {
+    if (a) {
+      return { b };
+    }
+  }, [a, b]);
+  return x;
+}