ARROW-13218: [Format] Clarify interpretation of timestamp values
ARROW-13218: [Format] Clarify interpretation of timestamp values

Try to make it clear how data is represented, and how it is to be interpreted (two possibly different things).

Also, replace "local date-time" with "naive date-time".

This is a followup to #10629.

Closes #10997 from pitrou/ARROW-13218-timestamp-interpretation

Authored-by: Antoine Pitrou <9359a4d812173b65a3a0094cd86363e79731a3c2@python.org>
Signed-off-by: Antoine Pitrou <9359a4d812173b65a3a0094cd86363e79731a3c2@python.org>

apache/arrow,wesm/arrow,icexelloss/arrow,icexelloss/arrow,apache/arrow,laurentgo/arrow,wesm/arrow,apache/arrow,laurentgo/arrow,apache/arrow,wesm/arrow,apache/arrow,icexelloss/arrow,kou/arrow,wesm/arrow,wesm/arrow,laurentgo/arrow,laurentgo/arrow,apache/arrow,icexelloss/arrow,kou/arrow,laurentgo/arrow,laurentgo/arrow,kou/arrow,wesm/arrow,laurentgo/arrow,kou/arrow,kou/arrow,icexelloss/arrow,kou/arrow,laurentgo/arrow,wesm/arrow,icexelloss/arrow,wesm/arrow,laurentgo/arrow,laurentgo/arrow,apache/arrow,laurentgo/arrow,icexelloss/arrow,kou/arrow,apache/arrow,kou/arrow,wesm/arrow,laurentgo/arrow,apache/arrow,apache/arrow,apache/arrow,wesm/arrow,icexelloss/arrow,icexelloss/arrow,kou/arrow,apache/arrow,laurentgo/arrow,wesm/arrow,kou/arrow,kou/arrow,laurentgo/arrow,kou/arrow,apache/arrow,icexelloss/arrow,icexelloss/arrow,icexelloss/arrow,icexelloss/arrow,wesm/arrow,kou/arrow,kou/arrow,icexelloss/arrow,wesm/arrow,apache/arrow,laurentgo/arrow,wesm/arrow