* Add test support for ESP32S2
* Add loop back test
* Support chip internal connection, no external wiring required.
* Delete the relevant codes of PDM of ESP32-S2 ll layer.
* fix dac dma mode issue
The existing Bluetooth examples are split as:
1. examples/bluetooth/bluedroid - Bluedroid Host (BT + BLE) examples
a. examples/bluetooth/bluedroid/classic_bt - Classic BT examples
b. examples/bluetooth/bluedroid/ble - BLE examples
c. examples/bluetooth/bluedroid/coex - Classic BT and BLE coex examples
d. examples/bluetooth/bluedroid/hci - VHCI and HCI UART examples
i. Rename ble_adv to controller_vhci_ble_adv and move it in hci folder
2. examples/bluetooth/nimble - NimBLE BLE Host + NimBLE Mesh examples
3. examples/bluetooth/esp_ble_mesh - ESP BLE Mesh examples
4. Update documentation references