feat: Create HTTPTransport

[gjenkins8]

Create a HTTPTransport that "round trips" go native http request/responses via Extism's internal HTTP request/response mechanism

[nilslice]

Thank you @gjenkins8! Letting the CI do its thing - but as for some feedback on the implementation, I think we should move this into something like a http/std.go package outside the pdk package. This way, when no http operations are needed, the net/http stuff should be eliminated by the compiler and can save a lot of bytes from the .wasm output.

Would you be open to that?

[gjenkins8]

Thank you @gjenkins8! Letting the CI do its thing - but as for some feedback on the implementation, I think we should move this into something like a http/std.go package outside the pdk package. This way, when no http operations are needed, the net/http stuff should be eliminated by the compiler and can save a lot of bytes from the .wasm output.

Would you be open to that?

Hey, thanks for the feedback. That makes sense to me, I can move. The big potential hiccup, is I am using private methods in the pdk (root) package. Let me see what I can do / will potentially need. ie. I might need to move some of the things in the pdk package into an internal package.

[gjenkins8]

a743206 is pretty significant. I moved memory related functionality into an internal/memory package, extism host http functionality into an internal/http package, then finally HTTPTransport into an http package.

As you may imagine, a lot of code movement was required for this. Ultimately, I think it might be worth splitting this PR into smaller PRs (refactors vs feature addition), but I've leave this up to reviewer(s) to decide if needed.

edit: I could also imagine there could be different ways to slice and dice these changes e.g. all host / wasmimport functions could be in an "internal/extismhost package. Open to feedback of course

[gjenkins8]

Unscientific datapoints:

this line increases the compiled wasm module size from 2.3Mib to 6.6Mib (big go, GOOS=wasip1):

http.DefaultTransport = &pdkhttp.HTTPTransport{}

and these three lines increase the compiled module size from 2.3Mib to 9.1Mib:

	http.DefaultTransport = &pdkhttp.HTTPTransport{}
	client := http.DefaultClient
	_, err := client.Head("https://jsonplaceholder.typicode.com/todos/1")

So it seems like a worthy goal have to HTTPTransport in its own separate package

[evacchi]

from what I can tell (I am not super-familiar with this codebase) the changes make sense, I'll refer to @mhmd-azeez and/or @nilslice for approval :)

[mhmd-azeez]

This unlocks a lot of REST client libraries, thank you very much!

[nilslice]

will get this out in the next release!