doc: Improve context for thread identity in scheduling

Enhance the description around reschedule points to provide more
context about the current thread's identity. This update clarifies
that changing the identity of the current thread involves switching
the CPU's execution from one thread to another.

Signed-off-by: Arrel Neumiller <rlneumiller@gmail.com>

doc: Improve context for thread identity in scheduling

Enhance the description around reschedule points to provide more
context about the current thread's identity. This update clarifies
that changing the identity of the current thread involves switching
the CPU's execution from one thread to another.

Signed-off-by: Arrel Neumiller <rlneumiller@gmail.com>