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-nrf/src/gpiote.rs

@@ -9,7 +9,7 @@ use embassy_sync::waitqueue::AtomicWaker;
 
 use crate::gpio::sealed::Pin as _;
 use crate::gpio::{AnyPin, Flex, Input, Output, Pin as GpioPin};
-use crate::interrupt::Interrupt;
+use crate::interrupt::InterruptExt;
 use crate::ppi::{Event, Task};
 use crate::{interrupt, pac, peripherals};
 
@@ -75,15 +75,15 @@ pub(crate) fn init(irq_prio: crate::interrupt::Priority) {
 
     // Enable interrupts
     #[cfg(any(feature = "nrf5340-app-s", feature = "nrf9160-s"))]
-    type Irq = interrupt::GPIOTE0;
+    let irq = interrupt::GPIOTE0;
     #[cfg(any(feature = "nrf5340-app-ns", feature = "nrf9160-ns"))]
-    type Irq = interrupt::GPIOTE1;
+    let irq = interrupt::GPIOTE1;
     #[cfg(any(feature = "_nrf52", feature = "nrf5340-net"))]
-    type Irq = interrupt::GPIOTE;
+    let irq = interrupt::GPIOTE;
 
-    Irq::unpend();
-    Irq::set_priority(irq_prio);
-    unsafe { Irq::enable() };
+    irq.unpend();
+    irq.set_priority(irq_prio);
+    unsafe { irq.enable() };
 
     let g = regs();
     g.events_port.write(|w| w);