Parquet: Support non-UTC timestamps

[rcaudy]

Running (in groovy):

t = io.deephaven.db.tables.utils.ParquetTools.readTable("/data/parquetFiles/eth_v2_p2_cBROTLI.parquet")

Would result in:

io.deephaven.UncheckedDeephavenException: Unable to read column [tpep_pickup_datetime]: TimestampLogicalType, isAdjustedToUTC=false, unit=MICROS not supported

If we didn't have a fortunate schema conversion error that effectively treats the timestamps as UTC. We would like to reverse the error and properly support zoned timestamps. Presumably we could specify a timezone in read instructions.

We do have limited support in: io.deephaven.db.v2.locations.parquet.topage.ToDBDateTimePageFromInt96
Likely the reference time zone used there should be moved out to ParquetInstructions. Then we just need to integrate those instructions into the Int96 support and into the more standard datetime fields.

[rcaudy]

Elaborating on the description, the code in io.deephaven.parquet.ParquetFileReader#buildChildren has the fortunate bug, vs. code in io.deephaven.parquet.tempfix.ParquetMetadataConverter#buildChildren which handles converted types correctly as far as I can tell.

[malhotrashivam]

Parquet handling of isAdjustedToUTC:

TIMESTAMP type has two extra fields: isAdjustedToUTC (= true/false), unit (= MILLIS/MICROS/NANOS).

• TIMESTAMP with isAdjustedToUTC=true is defined as the time elapsed since the Unix epoch. So we can translate such a instant to UTC time and then adjust it to local timezone. For example, TIMESTAMP(isAdjustedToUTC=true, unit=MILLIS) value of 172800000 corresponds to 1970-01-03 00:00:00 UTC and the corresponding local time will change according to timezone.
• TIMESTAMP with isAdjustedToUTC=false represents time fields in a local timezone, regardless of what local timezone is. For example, TIMESTAMP(isAdjustedToUTC=false, unit=MILLIS) value of 172800000 corresponds to 1970-01-03 00:00:00 in any timezone.

More details in official docs here.

[devinrsmith]

I think on a column-by-column basis we should be able to add in an assumed timezone; for example, the NYC taxi dataset e, we can assume that the timezone is NYC timezone. As it stands today, we read this in as a LocalDateTime.

[malhotrashivam]

Original issue completed as part of #4801.