Make interrupt module more standard.

- Move typelevel interrupts to a special-purpose mod: `embassy_xx::interrupt::typelevel`.
- Reexport the PAC interrupt enum in `embassy_xx::interrupt`.

This has a few advantages:
- The `embassy_xx::interrupt` module is now more "standard".
  - It works with `cortex-m` functions for manipulating interrupts, for example.
  - It works with RTIC.
- the interrupt enum allows holding value that can be "any interrupt at runtime", this can't be done with typelevel irqs.
- When "const-generics on enums" is stable, we can remove the typelevel interrupts without disruptive changes to `embassy_xx::interrupt`.

embassy-rp/src/adc.rs

@@ -3,14 +3,14 @@ use core::marker::PhantomData;
 use core::sync::atomic::{compiler_fence, Ordering};
 use core::task::Poll;
 
-use embassy_cortex_m::interrupt::{Binding, Interrupt};
 use embassy_sync::waitqueue::AtomicWaker;
 use embedded_hal_02::adc::{Channel, OneShot};
 
 use crate::gpio::Pin;
-use crate::interrupt::{self, ADC_IRQ_FIFO};
+use crate::interrupt::typelevel::Binding;
+use crate::interrupt::InterruptExt;
 use crate::peripherals::ADC;
-use crate::{pac, peripherals, Peripheral};
+use crate::{interrupt, pac, peripherals, Peripheral};
 static WAKER: AtomicWaker = AtomicWaker::new();
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -47,7 +47,7 @@ impl<'d> Adc<'d> {
 
     pub fn new(
         _inner: impl Peripheral<P = ADC> + 'd,
-        _irq: impl Binding<ADC_IRQ_FIFO, InterruptHandler>,
+        _irq: impl Binding<interrupt::typelevel::ADC_IRQ_FIFO, InterruptHandler>,
         _config: Config,
     ) -> Self {
         unsafe {
@@ -62,10 +62,8 @@ impl<'d> Adc<'d> {
         }
 
         // Setup IRQ
-        unsafe {
-            ADC_IRQ_FIFO::unpend();
-            ADC_IRQ_FIFO::enable();
-        };
+        interrupt::ADC_IRQ_FIFO.unpend();
+        unsafe { interrupt::ADC_IRQ_FIFO.enable() };
 
         Self { phantom: PhantomData }
     }
@@ -164,7 +162,7 @@ pub struct InterruptHandler {
     _empty: (),
 }
 
-impl interrupt::Handler<ADC_IRQ_FIFO> for InterruptHandler {
+impl interrupt::typelevel::Handler<interrupt::typelevel::ADC_IRQ_FIFO> for InterruptHandler {
     unsafe fn on_interrupt() {
         let r = Adc::regs();
         r.inte().write(|w| w.set_fifo(false));