New VA108xx Rust workspace structure + dependency updates

- The workspace is now a monorepo without submodules. The HAL, PAC and BSP
  are integrated directly
- Update all dependencies: embedded-hal v1 and RTIC v2

examples/simple/src/main.rs

@@ -0,0 +1,13 @@
+//! Dummy app which does not do anything.
+#![no_main]
+#![no_std]
+
+use cortex_m_rt::entry;
+use panic_rtt_target as _;
+
+#[entry]
+fn main() -> ! {
+    loop {
+        cortex_m::asm::nop();
+    }
+}