feat(init): add init crate with declarative boot manifest, boot sequence, supervisor and shutdown stubs

Also: make types from_raw/raw const fn, add create_process/kill/delegate/revoke to userspace syscall stubs.

crates/init/src/lib.rs

@@ -0,0 +1,6 @@
+#![no_std]
+
+pub mod boot;
+pub mod manifest;
+pub mod shutdown;
+pub mod supervisor;