[2.0.0] BtClassic Discovery with info without connect (#4811)

Hey guys,
so I wanted to do a BtClassic Discovery without the need to call connect
and to list all found devices on a display and continue work with that list.

I wasn't capable to test the example code with my file structure, but I did use the discovery already in some different situations.

However when I noted that the Bluedroid stack won't let me enforce an RfComm SPP connection to a GPS Device (Skytraxx 2 plus, I guess its interface is built so simple that it doesn't advertise its SPP over SDP), I will probably have to switch to BtStack (BlueKitchen) and stop on this side meanwhile

libraries/BluetoothSerial/src/BTAdvertisedDeviceSet.cpp

@@ -0,0 +1,78 @@
+/*
+ * BTAdvertisedDeviceSet.cpp
+ *
+ *  Created on: Feb 5, 2021
+ *      Author: Thomas M. (ArcticSnowSky)
+ */
+
+#include "sdkconfig.h"
+#if defined(CONFIG_BT_ENABLED)
+
+//#include <map>
+
+#include "BTAdvertisedDevice.h"
+//#include "BTScan.h"
+
+
+BTAdvertisedDeviceSet::BTAdvertisedDeviceSet() {
+	m_cod		       = 0;
+	m_name             = "";
+	m_rssi             = 0;
+
+	m_haveCOD	       = false;
+	m_haveName         = false;
+	m_haveRSSI         = false;
+} // BTAdvertisedDeviceSet
+
+BTAddress   BTAdvertisedDeviceSet::getAddress()    { return m_address; }
+uint32_t    BTAdvertisedDeviceSet::getCOD()        { return m_cod; }
+std::string BTAdvertisedDeviceSet::getName()       { return m_name; }
+int8_t      BTAdvertisedDeviceSet::getRSSI()	    { return m_rssi; }
+
+
+bool        BTAdvertisedDeviceSet::haveCOD()   { return m_haveCOD; }
+bool        BTAdvertisedDeviceSet::haveName()  { return m_haveName; }
+bool        BTAdvertisedDeviceSet::haveRSSI()  { return m_haveRSSI; }
+
+/**
+ * @brief Create a string representation of this device.
+ * @return A string representation of this device.
+ */
+std::string BTAdvertisedDeviceSet::toString() {
+	std::string res = "Name: " + getName() + ", Address: " + getAddress().toString();
+	if (haveCOD()) {
+		char val[6];
+		snprintf(val, sizeof(val), "%d", getCOD());
+		res += ", cod: ";
+		res += val;
+	}
+	if (haveRSSI()) {
+		char val[4];
+		snprintf(val, sizeof(val), "%d", getRSSI());
+		res += ", rssi: ";
+		res += val;
+	}
+	return res;
+} // toString
+
+
+void BTAdvertisedDeviceSet::setAddress(BTAddress address) {
+    m_address = address;
+}
+
+void BTAdvertisedDeviceSet::setCOD(uint32_t cod) {
+    m_cod     = cod;
+	m_haveCOD = true;
+}
+
+void BTAdvertisedDeviceSet::setName(std::string name) {
+    m_name     = name;
+	m_haveName = true;
+}
+
+void BTAdvertisedDeviceSet::setRSSI(int8_t rssi) {
+    m_rssi     = rssi;
+	m_haveRSSI = true;
+}
+
+#endif /* CONFIG_BT_ENABLED */