Merge #539

539: nrf: async usb r=Dirbaio a=jacobrosenthal

Frankensteined together from this old pr https://github.com/embassy-rs/embassy/pull/115 and nrf-usdb

~Doesnt currently work..~

Co-authored-by: Jacob Rosenthal <jacobrosenthal@gmail.com>

embassy-nrf/src/lib.rs

@@ -47,6 +47,13 @@ pub mod temp;
 pub mod timer;
 pub mod twim;
 pub mod uarte;
+#[cfg(any(
+    feature = "_nrf5340-app",
+    feature = "nrf52820",
+    feature = "nrf52833",
+    feature = "nrf52840"
+))]
+pub mod usb;
 #[cfg(not(feature = "_nrf5340"))]
 pub mod wdt;