When retrieving attribute handles using the 128bit base version of a 16 bit UUID some devices will
report "not found". This will attempt to convert the UUID to the 16bit version and try again.
* Adds `to16()` method to NimBLEUUID.
* 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.
