Add support for generating PAC for dual cores

* Chips that have multiple cores will be exposed as chipname_corename,
  i.e. stm32wl55jc_cm4
* Chips that have single cores will use the chip family as feature name
  and pick the first and only core from the list
* Add support for stm32wl55 chip family

examples/stm32l0/src/bin/blinky.rs

@@ -8,7 +8,10 @@
 
 #[path = "../example_common.rs"]
 mod example_common;
-use embassy_stm32::{rcc::*, gpio::{Level, Output}};
+use embassy_stm32::{
+    gpio::{Level, Output},
+    rcc::*,
+};
 use embedded_hal::digital::v2::OutputPin;
 use example_common::*;