Refactor include directives to use different paths for arduino/idf.

* Sets macros to allow compiling when Central role is enabled and Observer disabled, or Peripheral enabled and Broadcaster disabled.

* Adds a macro definition for CONFIG_NIMBLE_CPP_IDF to enable different include paths/functionality for IDF / Arduino.

src/NimBLERemoteCharacteristic.cpp

@@ -12,11 +12,8 @@
  *      Author: kolban
  */
 
-#include "sdkconfig.h"
-#if defined(CONFIG_BT_ENABLED)
-
 #include "nimconfig.h"
-#if defined( CONFIG_BT_NIMBLE_ROLE_CENTRAL)
+#if defined(CONFIG_BT_ENABLED) && defined(CONFIG_BT_NIMBLE_ROLE_CENTRAL)
 
 #include "NimBLERemoteCharacteristic.h"
 #include "NimBLEUtils.h"
@@ -819,6 +816,4 @@ int NimBLERemoteCharacteristic::onWriteCB(uint16_t conn_handle,
     return 0;
 }
 
-
-#endif // #if defined( CONFIG_BT_NIMBLE_ROLE_CENTRAL)
-#endif /* CONFIG_BT_ENABLED */
+#endif /* CONFIG_BT_ENABLED && CONFIG_BT_NIMBLE_ROLE_CENTRAL */