The goal is to allow custom configuration for `variants_dir` to define our own board variant directly in the project.

With this functionnality, we are now allowed to define in our projects a custom board **AND** a custom variant.
https://docs.platformio.org/en/latest/platforms/creating_board.html#custom-embedded-boards

Here is an example of how to define a custom board with custom variant:
```
my_project
├── boards
│   └── custom_esp32dev.json
└── variants
    └── custom-esp32dev
        └── pins_arduino.h
```

custom_esp32dev.json
```json
{
  "build": {
    "arduino":{
      "ldscript": "esp32_out.ld"
    },
    "core": "esp32",
    "extra_flags": "-DARDUINO_ESP32_DEV",
    "f_cpu": "240000000L",
    "f_flash": "40000000L",
    "flash_mode": "dio",
    "mcu": "esp32",
    "variants_dir": "variants",
    "variant": "custom-esp32dev"
  },
  "connectivity": [
    "wifi",
    "bluetooth",
    "ethernet",
    "can"
  ],
  "debug": {
    "openocd_board": "esp-wroom-32.cfg"
  },
  "frameworks": [
    "arduino",
    "espidf"
  ],
  "name": "My Custom Espressif ESP32 Dev Module",
  "upload": {
    "flash_size": "4MB",
    "maximum_ram_size": 327680,
    "maximum_size": 4194304,
    "require_upload_port": true,
    "speed": 460800
  },
  "url": "https://en.wikipedia.org/wiki/ESP32",
  "vendor": "Espressif"
}
```

https://github.com/espressif/arduino-esp32/issues/3652

Do not pollute the global namespace with generic names like 'config' by declaring global variables 'static'.

Fixes https://github.com/espressif/arduino-esp32/issues/4466

pgmspace.h missing 'pgm_get_far_address'

See #3960 for more details of the problem and the solution. I only implemented what was proposed in this ticket, as it solves my problem, which was the same as in this ticket. Credits for the code going to @etrinh ;-)

This also is a more consistence behaviour compared to esp8266, where it also is possible to restart the wifiserver immediately on the same port.

changed to log_d()

..because a firstLine = false; is missing ;)

ESP-IDF release/v3.3: 66d3783c8
esp-face: 420fc7e
esp32-camera: 0107093

Checks to see if a string is a key in the namespace. 

Fixes #4440

* fix typo in WiFiMulti

* clean up trailing spaces

* clean up script file used in cleaning
Co-authored-by: NMe No Dev <me-no-dev@users.noreply.github.com>

This patch fixes update timeouts (error #6) on slow HTTP/HTTPS links.

* Add more options to the AI thinker cam.

The reason is power saving and compatibility of cheap chines clones with crappy flash chips.

* improve & fix BLEScan when too many BLE devices
- when wantDuplicates, no need to check duplicate and no more insert into vector
- delete advertisedDevice when not insert into vector, fix memory leak
- add showParse when you just want raw advertised data

Closes #4111.
gcc: I was not able to find an arm64 build on espressif's website so I choosed to put the armhf version, even if this should works this is only ok as temporary, arm64 runs better on arm64 than armhf :)
esptool: being interpreted python its ok
mkspiff: need igrr/mkspiffs#74 to be merged and artifacts added in /package/package_esp32_index.template.json.

https://github.com/arduino/ArduinoCore-sam/pull/6/files

It is used here:
https://github.com/arduino-libraries/ArduinoMDNS/blob/master/MDNS.cpp#L150

Add sdkconfig option CONFIG_ARDUINO_UDP_TASK_PRIORITY, which sets the task priority for the UDP vtask." (#4131)

Remove device from Peer list if connection fails.

Only call onConnect callback if connection was successful.

Only call onDisconnect callback if the connection was previously connected (ESP_GATTC_DISCONNECT_EVT is fired on a unsuccessful connection attempt also).

Resolves a number of issues with phantom events and callbacks being fired.

::addPeerDevice and ::removePeerDevice are called with m_appId, so should ::updatePeerDevice as all use the same parameter for the underlying map's key.

fixes #4454

closes #4455