The Availability type of an instance. Potential values:
ZONAL: The instance serves data from only one zone. Outages in
that zone affect instance availability.
REGIONAL: The instance can serve data from more than one zone
in a region (it is highly available).
Values:
AVAILABILITY_TYPE_UNSPECIFIED (0):
This is an unknown Availability type.
ZONAL (1):
Zonal available instance.
REGIONAL (2):
Regional (or Highly) available instance.
