Better types for HttpClient

[bhollis]

1. Provide a type parameter to HttpClient so that it returns the correct return type instead of any.
2. Convert all query params to strings and omit undefined values, and give them the type Record<string, string> so they don't need to have anything done to them to be able to be passed into UrlSearchParams.

This will help nail some of the last any usage in the DIM codebase. Major version bump because the types are changing in a way that'll require some code fixes for consumers.

[robojumper]

2 looks good. For 1 I'm not sure I understand how consumers are expected to provide a differently typed HttpClient to each endpoint function individually without resorting to any though.

[bhollis]

Ah, yes. I didn't quite understand the difference in practice between HttpClient being a generic type, vs. being a non-generic type that references a generic function.

[bhollis]

OK, switched it up. This lines up with a working change on the DIM side.