feat(users/Profpatsch/netencode.rs): parse multiple stdin values

Adds support for parsing multiple netencode values from stdin.

This is overly complicated for my tastes, but I don’t see a better way
of writing this logic that does not read all of stdin before starting
to parse the first value.

A kingdom for a conduit.

Change-Id: Ia4f849d4096c43e887756b756d2a85d7f9cd380a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6631
Autosubmit: Profpatsch <mail@profpatsch.de>
Reviewed-by: Profpatsch <mail@profpatsch.de>
Tested-by: BuildkiteCI

users/Profpatsch/read-http.rs

@@ -220,7 +220,7 @@ fn write_dict<'buf, 'a>(
 }
 
 // iter helper
-
+// TODO: put into its own module
 struct Chunkyboi<T> {
     inner: T,
     buf: Vec<u8>,