Repro for scope merging bug

This is a repro for a bug that occurs when `enableMergeConsecutiveScopes` is 
enabled. Reminder that this feature is off by default and not enabled yet 
internally. 

I found this via #2121, where eliminating extraneous whitespace JSXText 
instructions meant that MergeConsecutiveScopes started merging a fixture 
differently, revealing a bug. This PR reproduces that case by keeping the 
identical structure, but using plain objects to represent the JSX elements 
instead of JSX syntax.

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/merge-consecutive-scopes-objects.expect.md

@@ -0,0 +1,138 @@
+
+## Input
+
+```javascript
+// @enableMergeConsecutiveScopes
+// This is a translation of the original merge-consecutive-scopes which uses plain objects
+// to describe the UI instead of JSX. The JSXText elements in that fixture happen to
+// prevent scome scopes from merging, which concealed a bug with the merging logic.
+// By avoiding JSX we eliminate extraneous instructions and more accurately test the merging.
+function Component(props) {
+  let [state, setState] = useState(0);
+  return [
+    { component: Title, props: { text: "Counter" } },
+    { component: "span", props: { children: [state] } },
+    {
+      component: "button",
+      props: {
+        "data-testid": "button",
+        onClick: () => setState(state + 1),
+        children: ["increment"],
+      },
+    },
+  ];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{}],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react"; // @enableMergeConsecutiveScopes
+// This is a translation of the original merge-consecutive-scopes which uses plain objects
+// to describe the UI instead of JSX. The JSXText elements in that fixture happen to
+// prevent scome scopes from merging, which concealed a bug with the merging logic.
+// By avoiding JSX we eliminate extraneous instructions and more accurately test the merging.
+function Component(props) {
+  const $ = useMemoCache(18);
+  const [state, setState] = useState(0);
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = { component: Title, props: { text: "Counter" } };
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  const c_1 = $[1] !== state;
+  let t1;
+  if (c_1) {
+    const t2 = [state];
+    t1 = { children: t2 };
+    $[1] = state;
+    $[2] = t1;
+  } else {
+    t1 = $[2];
+  }
+  const c_3 = $[3] !== t2;
+  if (c_3) {
+    t1 = { children: t2 };
+    $[3] = t2;
+    $[4] = t1;
+  } else {
+    t1 = $[4];
+  }
+  const c_5 = $[5] !== t1;
+  let t3;
+  if (c_5) {
+    t3 = { component: "span", props: t1 };
+    $[5] = t1;
+    $[6] = t3;
+  } else {
+    t3 = $[6];
+  }
+  const c_7 = $[7] !== state;
+  let t4;
+  if (c_7) {
+    t4 = () => setState(state + 1);
+    $[7] = state;
+    $[8] = t4;
+  } else {
+    t4 = $[8];
+  }
+  let t5;
+  if ($[9] === Symbol.for("react.memo_cache_sentinel")) {
+    t5 = ["increment"];
+    $[9] = t5;
+  } else {
+    t5 = $[9];
+  }
+  if ($[10] === Symbol.for("react.memo_cache_sentinel")) {
+    t5 = ["increment"];
+    $[10] = t5;
+  } else {
+    t5 = $[10];
+  }
+  const c_11 = $[11] !== t4;
+  let t6;
+  if (c_11) {
+    const t7 = { "data-testid": "button", onClick: t4, children: t5 };
+    t6 = { component: "button", props: t7 };
+    $[11] = t4;
+    $[12] = t6;
+  } else {
+    t6 = $[12];
+  }
+  const c_13 = $[13] !== t7;
+  if (c_13) {
+    t6 = { component: "button", props: t7 };
+    $[13] = t7;
+    $[14] = t6;
+  } else {
+    t6 = $[14];
+  }
+  const c_15 = $[15] !== t3;
+  const c_16 = $[16] !== t6;
+  let t8;
+  if (c_15 || c_16) {
+    t8 = [t0, t3, t6];
+    $[15] = t3;
+    $[16] = t6;
+    $[17] = t8;
+  } else {
+    t8 = $[17];
+  }
+  return t8;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{}],
+};
+
+```
+      

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/merge-consecutive-scopes-objects.js

@@ -0,0 +1,25 @@
+// @enableMergeConsecutiveScopes
+// This is a translation of the original merge-consecutive-scopes which uses plain objects
+// to describe the UI instead of JSX. The JSXText elements in that fixture happen to
+// prevent scome scopes from merging, which concealed a bug with the merging logic.
+// By avoiding JSX we eliminate extraneous instructions and more accurately test the merging.
+function Component(props) {
+  let [state, setState] = useState(0);
+  return [
+    { component: Title, props: { text: "Counter" } },
+    { component: "span", props: { children: [state] } },
+    {
+      component: "button",
+      props: {
+        "data-testid": "button",
+        onClick: () => setState(state + 1),
+        children: ["increment"],
+      },
+    },
+  ];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{}],
+};