pycardium/utime: add unix_time and unix_time_ms

This merge request adds functions for getting the current unix time (instead of only being able to set it).

Added functions:

• utime.unix_time()
• utime.unix_time_ms()

pycardium/modules/qstrdefs.h

@@ -52,6 +52,8 @@ Q(monotonic)
 Q(monotonic_ms)
 Q(time)
 Q(time_ms)
+Q(unix_time)
+Q(unix_time_ms)
 Q(set_time)
 Q(set_unix_time)