Add embassy-cortex-m crate.

- Move Interrupt and InterruptExecutor from `embassy` to `embassy-cortex-m`.
- Move Unborrow from `embassy` to `embassy-hal-common` (nothing in `embassy` requires it anymore)
- Move PeripheralMutex from `embassy-hal-common` to `embassy-cortex-m`.

embassy-stm32/src/rcc/h7.rs

@@ -1,6 +1,6 @@
 use core::marker::PhantomData;
 
-use embassy::util::Unborrow;
+use crate::Unborrow;
 use embassy_hal_common::unborrow;
 use stm32_metapac::rcc::vals::{Mco1, Mco2};
 

embassy-stm32/src/rcc/l5.rs

@@ -1,3 +1,5 @@
+use stm32_metapac::PWR;
+
 use crate::pac::rcc::vals::{Hpre, Msirange, Pllsrc, Ppre, Sw};
 use crate::pac::{FLASH, RCC};
 use crate::rcc::{set_freqs, Clocks};
@@ -295,6 +297,8 @@ impl Default for Config {
 }
 
 pub(crate) unsafe fn init(config: Config) {
+    PWR.cr1()
+        .modify(|w| w.set_vos(stm32_metapac::pwr::vals::Vos::RANGE0));
     let (sys_clk, sw) = match config.mux {
         ClockSrc::MSI(range) => {
             // Enable MSI