Increase kernel stack size to 2mb, move from cooperative to timer

preemption based scheduling, add correct save_lock on aarch64, add
simple IPC (read, write, manage), and simple and unsecure SHM, add
per-process kernel stacks, add copy_cstr_to_user, always use run_next
for aarch64, remove primitives from the kernel

kernel/Cargo.toml

@@ -9,6 +9,7 @@ test = false
 bench = false
 
 [dependencies]
+bitflags = "2.11.1"
 font8x8 = { version = "0.3.1", default-features = false }
 heapless = "0.9.2"
 lazy_static = { version = "1.5.0", features = ["spin_no_std"] }