ddl: fix DST times for adding index (#47425)

[ti-chi-bot]

This is an automated cherry-pick of #47425

What problem does this PR solve?

Issue Number: close #47426, ref #46033

Problem Summary:

I did not consider DST values in #46055. As a result, the timezone names are always ignored. It may cause data inconsistency when TiDB encounters DST values during adding index.

What is changed and how it works?

• Revert the changes in ddl: use the correct timezone to encode record for adding index #46055. I bring back timezone name because it determines whether DST rules are used.
• On the other hand, I try another way to fix Data inconsistency after adding index in ingest mode #46033: we don't return "UTC" as the default value when GetTimeZone() because TimeZoneLocation.GetLocation() could handle the empty strings properly. Thus, the priority between time_zone_name and time_zone_offset is preserved.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[Benjamin2037]

LGTM

[zimulala]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Benjamin2037, zimulala

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-10-08 07:38:50.493074495 +0000 UTC m=+951528.080184640: ☑️ agreed by Benjamin2037.
• 2023-10-08 07:39:29.671870172 +0000 UTC m=+951567.258980317: ☑️ agreed by zimulala.