[hotfix] use ltz_millis as paimon system column for timestamp datatype

[luoyuxia]

Purpose

Linked issue: close #xxx
Current, TIMESTAMP_WITH_LOCAL_TIME_ZONE() is actaul with presion 6, but fluss's record timestamp is only up to presion 3, so, need to use presion 6

Brief change log

Change to use TIMESTAMP_LTZ_MILLIS

Tests

API and Format

Documentation

[LiebingYu]

@luoyuxia I think it's not a hotfix. For example:

1. user create a lake table A with __timestamp of presion 6
2. user disable lake table of A
3. cluster upgrade with __timestamp of presion 3
4. user will fail to enable lake table A, since schema not match.

[LiebingYu]

+1