feat: add overload types for find service methods

[robbyphillips]

Summary

I thought this might be a better way to have a conversation about #1970.

The goal is to let typescript automatically infer the return type for find methods based on params.paginate.

I do not think it is dependent on any other PRs.

Other Information

Adding these type definitions did have one unexpected side effect where TS no longer approved of line 106 in packages/authentication-oauth/src/strategy.ts, but it was such a little change that I included it in this PR.

I can think of two things that I would really like some feeback on:

1. The main ServiceMethods<T> definition for find has the signature find (params?: Params): Promise<T | T[] | Paginated<T>>;, and the Promise<T> result is not included in the overloads

2. I am not sure if changes similar to the one in the strategy.ts file would be needed in some ecosystem libs

[robbyphillips]

Hey @daffl, just wondering if I should've done something different here. Totally get that something like this might be very low priority -- it just seems like a pretty straightforward "quality of life" improvement to me.

[daffl]

Sorry about that and thank you for the PR @robbyphillips. Been meaning to address this but I am also in the process of moving the adapters specific typings into https://github.com/feathersjs/databases and https://github.com/feathersjs/databases/tree/master/packages/adapter-commons

[robbyphillips]

No worries at all, just happy to contribute if it's helpful.

And thanks for pointing out where new work is happening. Is this part of a reorg with v5?