[FL-2627] Flipper applications: SDK, build and debug system (#1387)

* Added support for running applications from SD card (FAPs - Flipper Application Packages)
* Added plugin_dist target for fbt to build FAPs
* All apps of type FlipperAppType.EXTERNAL and FlipperAppType.PLUGIN are built as FAPs by default
* Updated VSCode configuration for new fbt features - re-deploy stock configuration to use them
* Added debugging support for FAPs with fbt debug & VSCode
* Added public firmware API with automated versioning

Co-authored-by: hedger <hedger@users.noreply.github.com>
Co-authored-by: SG <who.just.the.doctor@gmail.com>
Co-authored-by: あく <alleteam@gmail.com>

lib/digital_signal/digital_signal.h

@@ -6,6 +6,10 @@
 
 #include <furi_hal_gpio.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 typedef struct {
     bool start_level;
     uint32_t edge_cnt;
@@ -29,3 +33,7 @@ uint32_t digital_signal_get_edges_cnt(DigitalSignal* signal);
 uint32_t digital_signal_get_edge(DigitalSignal* signal, uint32_t edge_num);
 
 void digital_signal_send(DigitalSignal* signal, const GpioPin* gpio);
+
+#ifdef __cplusplus
+}
+#endif