refactor!: avoid using futures crate directly (#2117)

Due to the low maintenance and absurd high amount of `unsafe` code in
parts of the `futures` crate, we are trying to avoid usage of it.

Usages are replaced with

- `futures-lite` : general `Future` and `Stream` tooling
- `futures-sink`: `Sink` trait
- `futures-buffered`: faster and safer version of `Futures{Un}Ordered`
- If must be `futures-util` for sink specific things that are missing

## Breaking Changes

- `iroh::node::Node` does not implement `Future` anymore
- `iroh::node::Node::shutdown()` is now `async` and can be awaited upon
to wait for the node to exit
- `iroh_net::util::AbortingJoinHandle`s inner field is not public
anymore, use the `From<JoinHandle>` implementation to contruct it


## Followups

- [x] Apply this to `bao-tree`:
n0-computer/bao-tree#49
- [x] Apply this to `iroh-io`:
n0-computer/iroh-io#6
- [x] Apply this to `quic-rpc`:
n0-computer/quic-rpc#73

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Co-authored-by: Ruediger Klaehn <rklaehn@protonmail.com>