(v5) I'd like get a generic executor from `build.input.pgRegistry` inside a `makeExtendSchemaPlugin`.
I was directed here from Discord: https://discord.com/channels/489127045289476126/498852330754801666/1245437899022012607

### Summary

The docs show how to get an executor from a pgResource (where pgResources is simply going to be a list of exposed tables and functions in your postgres schema).


```typescript
export const ExamplePlugin = makeExtendSchemaPlugin((build) => {
  const { users } = build.input.pgRegistry.pgResources
  const { executor } = users
  return {
    plans: {
      Mutation: {
        example(_, fieldArgs) {
          const $input = fieldArgs.getRaw('input')
          const $result = withPgClientTransaction(
            executor,
            $input,
            async (pgClient, input) => {
              // ...
            }
          )
        }
      }
    }
  }
})
```

But it would be nice to be able to get a generic executor for the database instead of having to get one from specific tables, even if all of the executors for the same database actually are the same object.
