Fixes sporadic blocking of the wifi thread in esp_wifi_recv_cb function under heavy network load conditions when frames are coming in faster than they can be processed. Since esp_wifi_recv_cb function is not executed in interrupt context, the msg_send function used for ISR event can block when the message queue is full. With this change esp_wifi can be flooded with icmpv6 packets of maximum size without any problems over hours.

Add SAML10/SAML11 support through SAM0 because hardware IP are the same so reuse to avoid duplication

During flash write access, the IROM cache cannot be used and is disabled therefore. During that time, ets_post crashes if a functions is called which is not in IRAM. Therefore thread_flags_set must not be called if IROM cache is disabled.

With the new ETS task handling thread, the stack sizes could be down sized.

Changes of ETS task handling require the context switch by software interrupt. The context switch based on interrupt is therefore enabled by default. Furthermore, the number of priority levels are increased due to the new additional thread.

ETS tasks are now handled by a high priority RIOT thread

Since complete MAC frames are handled, ETHERNET_MAX_LEN has to be used instead of ETHERNET_DATA_LEN for buffer sizes and length checks.

Since complete MAC frames are handled, ETHERNET_MAX_LEN has to be used instead of ETHERNET_DATA_LEN for buffer sizes and length checks.

The type [is documented as `gnrc_nettype_t`][1] so it should by checked
as such.

[1]: https://github.com/RIOT-OS/RIOT/blob/f9a3bdf1a749f0e6a0d9e79eee652d8b31d4d9e0/sys/include/net/netopt.h#L210-L212

ESP-IDF heap handling has to be used for esp_wifi for stability reasons. Otherwise, heap is corrupted sporadically

Fixes sporadic blocking of the wifi thread in esp_wifi_recv_cb function under heavy network load conditions when frames are coming in faster than they can be processed. Since esp_wifi_recv_cb function is not executed in interrupt context, the msg_send function used for ISR event can block when the message queue is full. With this change esp_wifi can be flooded with icmpv6 packets of maximum size without any problems over hours.

To avoid further inconsistencies in documentation, README.md is not provided any longer

If WiFi is disconnected, e.g., because of timeout for beacon frame, it is tried to reconnect automatically.

RX callback function should be register when WiFi has been connected to AP successfully and should be unregistered when WiFi disconnects from AP. Therefore, esp_wifi_internal_reg_rxcb is called now in event handler on event SYSTEM_EVENT_STA_CONNECTED. It is reset now on event SYSTEM_EVENT_STA_DISCONNECTED.

Before function wifi_connect is executed, starting the WiFi driver should have been finished. This is indicated by the WiFi driver by sending event SYSTEM_EVENT_STA_START. Function wifi_connect is moved therefore to the event handler for SYSTEM_EVENT_STA_START.

The buffer given by the WiFi driver as parameter eb has to be freed explicitly. Otherwise the esp_wifi_netdev stops working after some seconds.

The WiFi configuration has to be static to avoid memory access problems when WiFi AP is reconnected.

esp_wifi was simply returning the connection state instead of filling the referenced value.