refactor: use include syntax for wasi:clocks

[Mossaka]

This commit uses include syntax to simplify the proxy world by hiding the interfaces from wasi:clock package

[lukewagner]

There's an interesting usability question here for how aggressively we want to use include to "factor out" imports between different proposals. For example, given the large number of interfaces in the WASI sockets proposal, include seems like a clear win. OTOH, if a proposal had one interface and one world, it would only add indirection (for the reader) to include the world instead of importing the interface. Cases like this PR are somewhere in the middle.

My impression is that, just looking at the before/after diff, the before state is more readable. However, I think that might just be superficially due to the name of the world: include wasi:clocks/example-world doesn't really tell me much. Just to pick a maybe-too-cute example, include wasi:clocks/support feels like it would be net more readable, so maybe we could pick that or some more helpful name than wasi:clocks/example-world?

[Mossaka]

Yeah totally agree that example-world isn't helpful. Pat made a suggestion to rename all the example-world to imports and I have a PR for each one of them (e.g. wasi:clocks: WebAssembly/wasi-clocks#49). If we think support world would be a better name, I am more than happy to change it.

[pchickey]

in a separate PR I suggested we rename example-world to imports. this is appropriate for poll, io, filesystem, sockets, clocks, and random. we should not export an imports world for http and cli.

[lukewagner]

Cool, I like imports.

[Mossaka]

I've updated the PR to use wasi:clocks/imports world.

[Mossaka]

Rebased

[lukewagner]

lgtm

[lukewagner]

lgtm. It'd be good to have @pchickey sign off too.