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.lock

@@ -7,6 +7,7 @@ name = "XunilOS"
 version = "0.1.0"
 dependencies = [
  "aarch64-cpu",
+ "bitflags",
  "fdt",
  "font8x8",
  "heapless",
@@ -36,9 +37,9 @@ checksum = "1e4b40c7323adcfc0a41c4b88143ed58346ff65a288fc144329c5c45e05d70c6"
 
 [[package]]
 name = "bitflags"
-version = "2.9.1"
+version = "2.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1b8e56985ec62d17e9c1001dc89c88ecd7dc08e47eba5ec7c29c7b5eeecde967"
+checksum = "c4512299f36f043ab09a583e57bceb5a5aab7a73db1805848e8fef3c9e8c78b3"
 
 [[package]]
 name = "byteorder"