avoid calling convex functions directly

[ldanilek]

Avoid calling convex functions -- queries/mutations/actions/httpactions -- directly, as if they were js functions. Instead, their _handler property is the js function, if it exists.

This avoids a new console.warn which was added to "convex/server" which happens if you call a registered query/mutation/action/httpaction directly.

I added some types, but i'm not sure if this makes it actually safer. the main benefit was not needing casts to make the PublicHttpAction type flow through from router.lookup

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[sshader]

slight preference for using mapped types instead of overloads but not blocking (e.g. https://github.com/get-convex/convex-test/compare/sshader-mapped-types?expand=1)