[Tracker] ESP32 support

[avtolstoy]

Description

This PR adds WiFi scanning support for Tracker. All other APIs except for WiFi interface state management and scanning are not available as of right now.

This feature branch should work with both the stock 0.0.6 ESP32 NCP firmware available from the factory, as well as with particle-iot/esp32-ncp-firmware#18.

Steps to Test

• wiring/no_fixture tests have been fixed to allow WiFi scanning on Tracker

1. WiFi scanning should work with stock 0.0.6 ESP32 NCP firmware
2. You should be able to grab a build from SDIO/Tracker support esp32-ncp-firmware#18 and update update over serial or OTA to 0.0.7 version (particle serial inspect should reflect that)
3. WiFi scanning should work with 0.0.7 ESP32 NCP firmware over muxed channel
4. 0.0.7 ESP32 NCP firmware should be updatable. Manually edit version.mk in SDIO/Tracker support esp32-ncp-firmware#18 and bump version to 0.0.8 and perform a clean build. Update OTA or using serial should work.

Example App

SYSTEM_THREAD(ENABLED);
SerialLogHandler dbg(LOG_LEVEL_ALL);

/* executes once at startup */
void setup() {
    WiFi.on();
}

/* executes continuously after setup() runs */
void loop() {
    WiFi.scan([](WiFiAccessPoint* result, void* cookie) -> void {
        char ssid[64] = {};
        memcpy(ssid, result->ssid, std::min<size_t>(sizeof(ssid) - 1, result->ssidLength));
        Log.info("Found SSID: %s (%02x:%02x:%02x:%02x:%02x:%02x)", ssid,
                result->bssid[0],
                result->bssid[1],
                result->bssid[2],
                result->bssid[3],
                result->bssid[4],
                result->bssid[5]);
    }, nullptr);
    delay(1000);
}

References

• SDIO/Tracker support esp32-ncp-firmware#18
• Do not clear external non-muxer shared event groups events on start gsm0710muxer#7

---

Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)

[avtolstoy]

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[YutingYou]

@avtolstoy Great reworking, since you've changed the transport layer, I was wondering have you run the stress test for OTA, this would be helpful for the stability of OTA and SDIO. The easiest way may be manually doing updating with CLI several times. Better to upgrade and downgrade.

[avtolstoy]

@YutingYou Yes, I've done that multiple times, you can see that there are some FIXMEs around XModem that were uncovered both here and in the NCP firmware. I've also listed updates as one of the main things to test :)

[XuGuohui]

This reminds me that in the system_network_manager.cpp, some of the APIs don't support more than one interface. We need to refactor them but we can do that later if they don't break things.