Move destructor back to .cpp file

Having it there (even defaulted, like this) means endpoint.hpp doesn't
have to include endpoint_state.hpp (which it otherwise would need,
because of the std::unique_ptr<EndpointState> default deleter
requirements).

llarp/service/endpoint.cpp

@@ -587,6 +587,10 @@ namespace llarp
       return true;
     }
 
+    // Keep this here (rather than the header) so that we don't need to include endpoint_state.hpp
+    // in endpoint.hpp for the unique_ptr member destructor.
+    Endpoint::~Endpoint() = default;
+
     bool
     Endpoint::PublishIntroSet(const EncryptedIntroSet& introset, AbstractRouter* r)
     {

llarp/service/endpoint.hpp

@@ -7,7 +7,6 @@
 #include <llarp/path/path.hpp>
 #include <llarp/path/pathbuilder.hpp>
 #include "address.hpp"
-#include "endpoint_state.hpp"
 #include "handler.hpp"
 #include "identity.hpp"
 #include "pendingbuffer.hpp"
@@ -62,6 +61,7 @@ namespace llarp
                       public EndpointBase
     {
       Endpoint(AbstractRouter* r, Context* parent);
+      ~Endpoint() override;
 
       /// return true if we are ready to recv packets from the void
       bool