testkit addPlugin behavior does not match envelop's

### Issue workflow progress

_Progress of the issue based on the
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- [ ] 1. The issue provides a
[minimal reproduction](https://en.wikipedia.org/wiki/Minimal_reproducible_example) available on
[Stackblitz](https://stackblitz.com/fork/node).
- _Please install the latest `@envelop/*` packages that you are using._
- _Please make sure the reproduction is as small as possible._
- [x] 2. A failing test has been provided
- [ ] 3. A local solution has been provided
- [ ] 4. A pull request is pending review

---

**Describe the bug**

`addPlugin` behavior differs for `createTestkit` vs passing plugins into `graphql-yoga`'s `createYoga`

**To Reproduce** Steps to reproduce the behavior:

```ts
import { useApolloTracing } from "@envelop/apollo-tracing";
import { handleStreamOrSingleExecutionResult } from "@envelop/core";

import { assertSingleExecutionValue, createTestkit } from "@envelop/testing";
import { makeExecutableSchema } from "@graphql-tools/schema";

const useExample = () => {
return {
onPluginInit({ addPlugin }) {
addPlugin(useApolloTracing());
},
onExecute() {
return {
onExecuteDone(payload) {
handleStreamOrSingleExecutionResult(payload, ({ result, args, setResult }) => {
// during test, this will log without the trace
// but during normal execution, this will log with the trace
console.log(result);
});
}
}
},
}
}

// JEST TEST
test("calls #track", async () => {
const schema = makeExecutableSchema({
typeDefs: `
type Query {
foo: String
}
`,
resolvers: {
Query: {
foo: jest.fn().mockResolveValue("ok"),
},
},
});
const testInstance = createTestkit([useExample()], schema);
const result = await testInstance.execute(`{ errors }`);
});
```

**Expected behavior**

test kit flow call order should match yoga server / envelop server.
In both cases for the example above, the result should include the trace data.

**Environment:**

- OS:
- NodeJS:
- `@envelop/*` versions:
- `@envelop/core`: `5.0.0`
- `graphql-yoga`: `5.1.1`
- `envelop/testing`: `7.0.0`

**Additional context**

If instead of implementing onExecute, I use `addPlugin` to add the same logic, it calls in the expected order from the testkit