tests: arch: arm_thread_swap: extend the test for Cortex-M Baseline

We rework the arm_thread_swap test, so it can build
and run for Cortex-M Basline architecture (Cortex-M0,
Cortex-M0+, and Cortex-M23). In most cases, this rework
involved re-implementing the code blocks for storing
and loading the callee-saved registers to and from
memory. In addition, we skip the verification of
BASEPRI, and replace it with verifying PRIMASK.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>