Experiment: C++17 support (#9874)

* Add C++17 support

* Add C++17 runtime probes and update build configurations for STM32 and Portduino

* Remove unflags

* Update C++ standard flags across the platforms

* Convert a couple of instances to structured bindings

* NRF52 platform.txt to add C++17 support

* Still need the unflags apparently

* Remove C++17 runtime probe tests from test_main.cpp

* Reconfigured doesnt need a nodiscard

* Remove nodiscard attribute from init() method in RadioInterface

* Remove mbedtls/error.h from build flags

Removed include directive for mbedtls/error.h from build flags.

* Fix IRAM overflow

* Fix IRAM overflow

* Add build flag to exclude MQTT from rak11200

* Update C++ standard from gnu17 to gnu++17

src/mesh/Router.h

@@ -58,14 +58,14 @@ class Router : protected concurrency::OSThread, protected PacketHistory
     /** Allocate and return a meshpacket which defaults as send to broadcast from the current node.
      * The returned packet is guaranteed to have a unique packet ID already assigned
      */
-    meshtastic_MeshPacket *allocForSending();
+    [[nodiscard]] meshtastic_MeshPacket *allocForSending();
 
     /** Return Underlying interface's TX queue status */
-    meshtastic_QueueStatus getQueueStatus();
+    [[nodiscard]] meshtastic_QueueStatus getQueueStatus();
 
     /**
      * @return our local nodenum */
-    NodeNum getNodeNum();
+    [[nodiscard]] NodeNum getNodeNum();
 
     /** Wake up the router thread ASAP, because we just queued a message for it.
      * FIXME, this is kinda a hack because we don't have a nice way yet to say 'wake us because we are 'blocked on this queue'