doc: releases: update migration guide for the struct arch_esf

Add a note about the introduction of `struct arch_esf` and the
deprecation of `z_arch_esf_t`.

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

Author: ycsin

doc/releases/migration-guide-3.7.rst

@@ -59,6 +59,11 @@ Build System
 Kernel
 ******
 
+* All architectures are now required to define the new ``struct arch_esf``, which describes the members
+  of a stack frame. This new struct replaces the named struct ``z_arch_esf_t``. (:github:`73593`)
+
+* The named struct ``z_arch_esf_t`` is now deprecated. Use ``struct arch_esf`` instead. (:github:`73593`)
+
 Boards
 ******