datetime functions fix to return the correct timezone value

[Artem-OSSRevival]

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number: #5894 #5735

Description:

The date() and tostring() functions return the value without taking into account the user's time zone offset, while other functions, datetime() and time(), do this. The output has different values.

Fixed return values ​​of functions: date(), tostring(date()), tostring(datetime()), tostring(time()). Now the values ​​returned by them correspond to other ones like datetime() or time().

How do you solve it?

Added the time zone offset performing to the functions.

Special notes for your reviewer, ex. impact of this fix, design document, etc:

To reproduce: add “--timezone_name=UTC+11:00“ (or +12, so there is some offset to a time after midnight [next day]) to “/usr/local/nebula/etc/nebula-graphd.conf” and then start the nebula services.

Before:

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After:

Unit Tests:

Checklist:

Tests:

• Unit test (positive and negative cases)
• Function test
• Performance test
• N/A

Affects:

• Documentation affected (Please add the label if documentation needs to be modified.)
• Incompatibility (If it breaks the compatibility, please describe it and add the label.）
• If it's needed to cherry-pick (If cherry-pick to some branches is required, please label the destination version(s).)
• Performance impacted: Consumes more CPU/Memory

Release notes:

Fixed the bug of returning the incorrect timezone values.