Figure out `jest` memory leaks

While adding CI for different versions https://github.com/dotansimha/graphql-code-generator/pull/8013 the CI on node 18 was failing.

After investigating as we run more tests the memory usage just keeps going up
```
yarn test --logHeapUsage --runInBand
```

Locally I tried running global garbage collector after each tests which seem to reduce some usage but https://github.com/dotansimha/graphql-code-generator/pull/8013/commits/93a0067a275ba456fea55efb7ad36f09f7112dc8 it still isn't enough

We need to investigate ways we can fix this properly.