[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/BTAdvertisedDevice.h

@@ -0,0 +1,65 @@
+/*
+ * BTAdvertisedDevice.h
+ *
+ *  Created on: Feb 5, 2021
+ *      Author: Thomas M. (ArcticSnowSky)
+ */
+
+#ifndef __BTADVERTISEDDEVICE_H__
+#define __BTADVERTISEDDEVICE_H__
+
+#include "BTAddress.h"
+
+
+class BTAdvertisedDevice {
+public:
+    virtual ~BTAdvertisedDevice() = default;
+
+    virtual BTAddress   getAddress();
+    virtual uint32_t    getCOD();
+    virtual std::string getName();
+    virtual int8_t      getRSSI();
+
+
+    virtual bool        haveCOD();
+    virtual bool        haveName();
+    virtual bool        haveRSSI();
+
+    virtual std::string toString();
+};
+
+class BTAdvertisedDeviceSet : public virtual BTAdvertisedDevice {
+public:
+    BTAdvertisedDeviceSet();
+    //~BTAdvertisedDeviceSet() = default;
+    
+
+    BTAddress   getAddress();
+    uint32_t    getCOD();
+    std::string getName();
+    int8_t      getRSSI();
+
+
+    bool        haveCOD();
+    bool        haveName();
+    bool        haveRSSI();
+
+    std::string toString();
+
+    void setAddress(BTAddress address);
+    void setCOD(uint32_t cod);
+    void setName(std::string name);
+    void setRSSI(int8_t rssi);
+
+    bool m_haveCOD;
+    bool m_haveName;
+    bool m_haveRSSI;
+
+
+    BTAddress   m_address = BTAddress((uint8_t*)"\0\0\0\0\0\0");
+    uint32_t    m_cod;
+    std::string m_name;
+    int8_t      m_rssi;
+};
+
+#endif