from carbon-clickhouse, port of SlowTimestampToDays, broken symmetic, not always UTC.

from carbon-clickhouse, port of SlowTimestampToDays, broken symmetic, not always UTC.

MaxTimestampToDaysFormat return formatted maximum (local, UTC) date.

MaxTimeToDaysFormat return formatted maximum (local, UTC) date.

MinTimestampToDaysFormat return formatted minimum (local, UTC) date.

MinTimeToDaysFormat return formatted minimum (local, UTC) date.

SetBoth() is for mixed SlowTimestampToDays/UTCTimestampToDays (before rebuild tables complete).

SetDefault() is for broken SlowTimestampToDays in carbon-clickhouse.

SetUTC() is for UTCTimestampToDays in carbon-clickhouse (see https://github.com/go-graphite/carbon-clickhouse/pull/114).