task_local context over context objects

- interner impls logically separate from API in orchid-base (default host interner still in base for testing)
- error reporting, logging, and a variety of other features passed down via context in extension, not yet in host to maintain library-ish profile, should consider options
- no global spawn mechanic, the host has a spawn function but extensions only get a stash for enqueuing async work in sync callbacks which is then explicitly, manually, and with strict order popped and awaited
- still deadlocks nondeterministically for some ungodly reason

orchid-base/src/localset.rs

@@ -0,0 +1,48 @@
+use std::collections::VecDeque;
+use std::pin::Pin;
+use std::task::Poll;
+
+use futures::StreamExt;
+use futures::channel::mpsc::{UnboundedReceiver, UnboundedSender, unbounded};
+use futures::future::LocalBoxFuture;
+
+pub struct LocalSet<'a, E> {
+	receiver: UnboundedReceiver<LocalBoxFuture<'a, Result<(), E>>>,
+	pending: VecDeque<LocalBoxFuture<'a, Result<(), E>>>,
+}
+impl<'a, E> LocalSet<'a, E> {
+	pub fn new() -> (UnboundedSender<LocalBoxFuture<'a, Result<(), E>>>, Self) {
+		let (sender, receiver) = unbounded();
+		(sender, Self { receiver, pending: VecDeque::new() })
+	}
+}
+impl<E> Future for LocalSet<'_, E> {
+	type Output = Result<(), E>;
+	fn poll(self: Pin<&mut Self>, cx: &mut std::task::Context<'_>) -> Poll<Self::Output> {
+		let this = self.get_mut();
+		let mut any_pending = false;
+		loop {
+			match this.receiver.poll_next_unpin(cx) {
+				Poll::Pending => {
+					any_pending = true;
+					break;
+				},
+				Poll::Ready(None) => break,
+				Poll::Ready(Some(fut)) => this.pending.push_back(fut),
+			}
+		}
+		let count = this.pending.len();
+		for _ in 0..count {
+			let mut req = this.pending.pop_front().unwrap();
+			match req.as_mut().poll(cx) {
+				Poll::Ready(Ok(())) => (),
+				Poll::Ready(Err(e)) => return Poll::Ready(Err(e)),
+				Poll::Pending => {
+					any_pending = true;
+					this.pending.push_back(req)
+				},
+			}
+		}
+		if any_pending { Poll::Pending } else { Poll::Ready(Ok(())) }
+	}
+}