x/build/cmd/relui: simplify HTTP route handling code by using net/http's pattern matching #76860
Description
The route handling code in relui was added before net/http was enhanced with pattern matching in Go 1.22 (https://go.dev/doc/go1.22#enhanced_routing_patterns). Relui can rely on 1.22+ being available (its go.mod has go 1.24.0+), so it might be possible to simplify its code by using that. Filing this issue for that.
Also noting here that some of the route registration uses task names, which we've recently realized may contain "/" characters, and those will need some thought to handle.
CC @golang/release.