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-stm32/src/i2c/v2.rs

@@ -3,7 +3,6 @@ use core::future::poll_fn;
 use core::marker::PhantomData;
 use core::task::Poll;
 
-use embassy_cortex_m::interrupt::Interrupt;
 use embassy_embedded_hal::SetConfig;
 use embassy_hal_common::drop::OnDrop;
 use embassy_hal_common::{into_ref, PeripheralRef};
@@ -13,6 +12,7 @@ use crate::dma::{NoDma, Transfer};
 use crate::gpio::sealed::AFType;
 use crate::gpio::Pull;
 use crate::i2c::{Error, Instance, SclPin, SdaPin};
+use crate::interrupt::typelevel::Interrupt;
 use crate::pac::i2c;
 use crate::time::Hertz;
 use crate::{interrupt, Peripheral};
@@ -22,7 +22,7 @@ pub struct InterruptHandler<T: Instance> {
     _phantom: PhantomData<T>,
 }
 
-impl<T: Instance> interrupt::Handler<T::Interrupt> for InterruptHandler<T> {
+impl<T: Instance> interrupt::typelevel::Handler<T::Interrupt> for InterruptHandler<T> {
     unsafe fn on_interrupt() {
         let regs = T::regs();
         let isr = regs.isr().read();
@@ -78,7 +78,7 @@ impl<'d, T: Instance, TXDMA, RXDMA> I2c<'d, T, TXDMA, RXDMA> {
         peri: impl Peripheral<P = T> + 'd,
         scl: impl Peripheral<P = impl SclPin<T>> + 'd,
         sda: impl Peripheral<P = impl SdaPin<T>> + 'd,
-        _irq: impl interrupt::Binding<T::Interrupt, InterruptHandler<T>> + 'd,
+        _irq: impl interrupt::typelevel::Binding<T::Interrupt, InterruptHandler<T>> + 'd,
         tx_dma: impl Peripheral<P = TXDMA> + 'd,
         rx_dma: impl Peripheral<P = RXDMA> + 'd,
         freq: Hertz,