Update dependencies, allow disabling HTTP2, don't depend on twilight-http

[Gelbpunkt]

Changes:

• Minor dependency updates (dashmap, hyper-rustls, metrics-exporter-prometheus)
• Use the new twilight-http-ratelimiting crate instead of twilight-http to relieve dependency amounts
• Using the new hyper-rustls ConnectorBuilder, allow disabling HTTP2 via a new DISABLE_HTTP2 enviroment variable due to hyper connection pooling issues (http2 GOAWAY causes client to drop requests hyperium/hyper#2500, Http2: Hyper client gets stuck if too many requests are spawned hyperium/hyper#2419)
• Use hyper-trust-dns for a non-blocking DNS resolver (this can't be changed easily at runtime due to types, else I would have made an opt-out flag)
• Add descriptions for the new variants of Path

[Erk-]

Just some small nits