doc: updated release note & migration guide for the kernel thread cmd

Added entries in the release note & migration guide about the
changes to the `kernel thread` shell command.

Signed-off-by: Yong Cong Sin <[email protected]>
Signed-off-by: Yong Cong Sin <[email protected]>

Author: ycsin

doc/releases/migration-guide-4.0.rst

@@ -210,5 +210,11 @@ MCUmgr
 Modem
 =====
 
+Shell
+=====
+
+* ``kernel threads`` and ``kernel stacks`` shell command have been renamed to
+  ``kernel thread list`` & ``kernel thread stacks``
+
 Architectures
 *************

doc/releases/release-notes-4.0.rst

@@ -302,6 +302,13 @@ Libraries / Subsystems
 
 * SD
 
+* Shell:
+
+  * Reorganized the ``kernel threads`` and ``kernel stacks`` shell command under the
+    L1 ``kernel thread`` shell command as ``kernel thread list`` & ``kernel thread stacks``
+  * Added multiple shell command to configure the CPU mask affinity / pinning a thread in
+    runtime, do ``kernel thread -h`` for more info.
+
 * State Machine Framework
 
 * Storage