Switch to crates.io embedded-hal, embedded-hal-async.

This temporarily removes support for the async UART trait, since it's
not yet in embedded-hal-async.

examples/stm32l4/src/bin/usart_blocking_async.rs

@@ -1,30 +0,0 @@
-#![no_std]
-#![no_main]
-#![feature(type_alias_impl_trait)]
-
-use defmt_rtt as _; // global logger
-use panic_probe as _;
-
-use defmt::*;
-use embassy::executor::Spawner;
-use embassy_stm32::dma::NoDma;
-use embassy_stm32::usart::{Config, Uart};
-use embassy_stm32::Peripherals;
-use embassy_traits::adapter::BlockingAsync;
-use embedded_hal_async::serial::{Read, Write};
-
-#[embassy::main]
-async fn main(_spawner: Spawner, p: Peripherals) {
-    let config = Config::default();
-    let usart = Uart::new(p.UART4, p.PA1, p.PA0, NoDma, NoDma, config);
-    let mut usart = BlockingAsync::new(usart);
-
-    unwrap!(usart.write(b"Hello Embassy World!\r\n").await);
-    info!("wrote Hello, starting echo");
-
-    let mut buf = [0u8; 1];
-    loop {
-        unwrap!(usart.read(&mut buf).await);
-        unwrap!(usart.write(&buf).await);
-    }
-}