Explore replacing default agenttime.c adapter

[sandeepmistry]

From discussion in #16 (comment)

The default agenttime.c is currently used, and then the POSIX based time layer is implemented in src/samd/time.cpp using RTCZero on SAMD.

We should explore using a custom agenttime.h implementation that is backed by the NTPClient. This would remove the dependency on RTCZero as the NTPClient can auto-sync the time with the NTP server at a preconfigured interval.

Then a UDP instance or NTPClient instance could be passed in the constructor. Another added benefit is the library is portable to any Arduino board that provides a SSLClient type and UDP type.

[tameraw]

@sandeepmistry - We're looking at possibly setting up the NTP services during Platform_init().

[JetstreamRoySprowl]

Good stuff, @sandeepmistry. We've captured this in our backlog as an improvement to make. Thank you!