Load .rrd file over HTTP

[emilk]

Minimal working version.

It does not stream over HTTP - it downloads the full .rrd file before decoding it.

The .rrd file is then decoded progressively (important, since the decoding is pretty slow on web).

Tested on web and native.

Part of #1494

Test native with cargo r -p rerun -- some.rrd

Test web with:

python3 examples/python/colmap/main.py --dataset colmap_fiat --resize 800x600 --save web_viewer/fiat.rrd
cargo r -p re_build_web_viewer -- --release
(cd web_viewer && basic-http-server --addr 127.0.0.1:1234)

open "http://127.0.0.1:1234/?url=fiat.rrd"

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct

[emilk]

Issue filed at rustwasm/wasm-bindgen#3359

[jleibs]

Generally looks good, but could use a bit of cleanup for the edge-cases around how we match a URL to a given handler.