Update on "compiler: Log metrics on pruned memo blocks/values"

Adds additional information to the CompileSuccess LoggerEvent:
* `prunedMemoBlocks` is the number of reactive scopes that were pruned for some reason.
* `prunedMemoValues` is the number of unique _values_ produced by those scopes.

Both numbers exclude blocks that are just a hook call - ie although we create and prune a scope for eg `useState()`, that's just an artifact of the sequencing of our pipeline. So what this metric is counting is cases of _other_ values that go unmemoized. See the new fixture, which takes advantage of improvements in the snap runner to optionally emit the logger events in the .expect.md file if you include the "logger" pragma in a fixture.

[ghstack-poisoned]

Author: josephsavona

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Program.ts

@@ -329,6 +329,7 @@ export function compileProgram(
         fnName: compiledFn.id?.name ?? null,
         memoSlots: compiledFn.memoSlotsUsed,
         memoBlocks: compiledFn.memoBlocks,
+        memoValues: compiledFn.memoValues,
         prunedMemoBlocks: compiledFn.prunedMemoBlocks,
         prunedMemoValues: compiledFn.prunedMemoValues,
       });

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/CodegenReactiveFunction.ts

@@ -69,6 +69,11 @@ export type CodegenFunction = {
    */
   memoBlocks: number;
 
+  /**
+   * Number of memoized values across all reactive scopes
+   */
+  memoValues: number;
+
   /**
    * The number of reactive scopes that were created but had to be discarded
    * because they contained hook calls.
@@ -297,15 +302,17 @@ function codegenReactiveFunction(
     generator: fn.generator,
     async: fn.async,
     memoSlotsUsed: cx.nextCacheIndex,
-    memoBlocks: countMemoBlockVisitor.count,
+    memoBlocks: countMemoBlockVisitor.memoBlocks,
+    memoValues: countMemoBlockVisitor.memoValues,
     prunedMemoBlocks: countMemoBlockVisitor.prunedMemoBlocks,
     prunedMemoValues: countMemoBlockVisitor.prunedMemoValues,
   });
 }
 
 class CountMemoBlockVisitor extends ReactiveFunctionVisitor<void> {
   env: Environment;
-  count: number = 0;
+  memoBlocks: number = 0;
+  memoValues: number = 0;
   prunedMemoBlocks: number = 0;
   prunedMemoValues: number = 0;
 
@@ -314,9 +321,10 @@ class CountMemoBlockVisitor extends ReactiveFunctionVisitor<void> {
     this.env = env;
   }
 
-  override visitScope(scope: ReactiveScopeBlock, state: void): void {
-    this.count += 1;
-    this.traverseScope(scope, state);
+  override visitScope(scopeBlock: ReactiveScopeBlock, state: void): void {
+    this.memoBlocks += 1;
+    this.memoValues += scopeBlock.scope.declarations.size;
+    this.traverseScope(scopeBlock, state);
   }
 
   override visitPrunedScope(