[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/BTScanResultsSet.cpp

@@ -0,0 +1,95 @@
+/*
+ * BTScanResultsSet.cpp
+ *
+ *  Created on: Feb 5, 2021
+ *      Author: Thomas M. (ArcticSnowSky)
+ */
+
+#include "sdkconfig.h"
+#if defined(CONFIG_BT_ENABLED)
+
+
+#include <esp_err.h>
+
+#include "BTAdvertisedDevice.h"
+#include "BTScan.h"
+//#include "GeneralUtils.h"
+#include "esp32-hal-log.h"
+
+
+class BTAdvertisedDevice;
+
+/**
+ * @brief Dump the scan results to the log.
+ */
+void BTScanResultsSet::dump(Print *print) {
+	int cnt = getCount();
+	if (print == nullptr) {
+		log_v(">> Dump scan results : %d", cnt);
+		for (int i=0; i < cnt; i++) {
+			BTAdvertisedDevice* dev = getDevice(i);
+			if (dev)
+				log_d("- %d: %s\n", i+1, dev->toString().c_str());
+			else
+				log_d("- %d is null\n", i+1);
+		}
+		log_v("-- dump finished --");
+	} else {
+		print->printf(">> Dump scan results: %d\n", cnt);
+		for (int i=0; i < cnt; i++) {
+			BTAdvertisedDevice* dev = getDevice(i);
+			if (dev)
+				print->printf("- %d: %s\n", i+1, dev->toString().c_str());
+			else
+				print->printf("- %d is null\n", i+1);
+		}
+		print->println("-- Dump finished --");
+	}
+} // dump
+
+
+/**
+ * @brief Return the count of devices found in the last scan.
+ * @return The number of devices found in the last scan.
+ */
+int BTScanResultsSet::getCount() {
+	return m_vectorAdvertisedDevices.size();
+} // getCount
+
+
+/**
+ * @brief Return the specified device at the given index.
+ * The index should be between 0 and getCount()-1.
+ * @param [in] i The index of the device.
+ * @return The device at the specified index.
+ */
+BTAdvertisedDevice* BTScanResultsSet::getDevice(uint32_t i) {
+	if (i < 0)
+		return nullptr;
+
+	uint32_t x = 0;
+	BTAdvertisedDeviceSet* pDev = &m_vectorAdvertisedDevices.begin()->second;
+	for (auto it = m_vectorAdvertisedDevices.begin(); it != m_vectorAdvertisedDevices.end(); it++) {
+		pDev = &it->second;
+		if (x==i)	break;
+		x++;
+	}
+	return x==i ? pDev : nullptr;
+}
+
+void BTScanResultsSet::clear() {
+    //for(auto _dev : m_vectorAdvertisedDevices)
+	//	delete _dev.second;
+	m_vectorAdvertisedDevices.clear();
+}
+
+bool BTScanResultsSet::add(BTAdvertisedDeviceSet advertisedDevice, bool unique) {
+	std::string key = advertisedDevice.getAddress().toString();
+	if (!unique || m_vectorAdvertisedDevices.count(key) == 0) {
+		m_vectorAdvertisedDevices.insert(std::pair<std::string, BTAdvertisedDeviceSet>(key, advertisedDevice));
+		return true;
+	} else
+		return false;
+}
+
+#endif