If module `core_mutex_priority_inheritance` is enabled, the scheduling has to be active to lock/unlock the mutex/rmutex used by FreeRTOS semaphores. If scheduling is not active FreeRTOS semaphore function always succeed.
When FreeRTOS semaphores, as required by ESP-IDF, are used together with `gnrc_netif`, RIOT may crash if `STATUS_RECEIVE_BLOCKED` is used as a blocking mechanism in the FreeRTOS adaptation layer. The reason for this is that `gnrc_netif` uses thread flags since PR #16748. If the `gnrc_netif` thread is blocked because of a FreeRTOS semaphore, and is thus in `STATUS_RECEIVE_BLOCKED` state, the `_msg_send` function will cause a crash because it then assumes that `target->wait_data` contains a pointer to a message of type `msg_t`, but by using thread flags it contains the flag mask. This situation can happen if the ESP hardware is used while another thread is sending something timer controlled to the `gnrc_netif` thread.
To solve this problem `STATUS_MUTEX_LOCKED` is used instead of `STATUS_RECEIVE_BLOCKED` and `STATUS_SEND_BLOCKED`
Declare sched_active_thread and sched_active_pid locally in the ESP code for
now. Once the code is cleaned up to no longer tap into scheduler internals but
use the API instead, those can be dropped again.
