Nikolay Agishev

Regarding recent changes in general MPU configuration (https://github.com/zephyrproject-rtos/zephyr/pull/71969), add appropriate configs for isolating thread stacks into ARC MPU.

ARCMWDT: Fix issues with posix types

1

Fix posix pid_t type redifiniton (zephyr vs arcmwdtlib). Add omitted in arcmwdtlib type sigevent. This Fixes https://github.com/zephyrproject-rtos/zephyr/issues/75105

ARCMWDT: Some of POSIX tests are broken

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**Describe the bug** POSIX-compatible tests are broken for ARCMWDT compiler. Some types are not presented in MW library, some types mismatch with defined in Zephyr. **To Reproduce** Steps to reproduce...