perf(reactivity): improve reactive effect memory usage (#4001)

Based on #2345 , but with smaller API change

- Use class implementation for `ReactiveEffect`
- Switch internal creation of effects to use the class constructor
- Avoid options object allocation
- Avoid creating bound effect runner function (used in schedulers) when not necessary.
- Consumes ~17% less memory compared to last commit
- Introduces a very minor breaking change: the `scheduler` option passed to `effect` no longer receives the runner function.

packages/reactivity/__tests__/readonly.spec.ts

@@ -382,7 +382,7 @@ describe('reactivity/readonly', () => {
     const eff = effect(() => {
       roArr.includes(2)
     })
-    expect(eff.deps.length).toBe(0)
+    expect(eff.effect.deps.length).toBe(0)
   })
 
   test('readonly should track and trigger if wrapping reactive original (collection)', () => {