Switch request reflector backend

[athomason]

Requests to http-me.glitch.me occasionally fail with 500 errors, leading to test flakes [1]. @BrooksCunningham suggests using the nearly compatible http.edgecompute.app [2] instead, which seems to be more reliable and substantially faster thanks to being hosted directly on Fastly Compute.

One required change is not sending invalid UTF-8 in the request body, which results in a 500 Internal Server Error.

1. https://github.com/fastly/compute-sdk-go/actions/runs/8839087224/job/24271648933
2. https://github.com/BrooksCunningham/http-me-rust

[joeshaw]

I bulk-changed httpbin.com at one point to http-me.glitch.me, so a similar bulk change to http.edgecompute.app would be a good idea.

[athomason]

It would be easy to change the examples with the exception of e.g. "https://http-me.glitch.me/drip=2?wait=3000", // delay 3s + stream body 2s = 5s; the delay functionality isn't in http.edgecompute.app. I'll check how much work that would be to add.