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

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Benjamin2037, wjhuang2016

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [wjhuang2016]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-10-08 07:40:59.740827893 +0000 UTC m=+951657.327938023: ☑️ agreed by Benjamin2037.
• 2023-10-12 09:52:49.135092612 +0000 UTC m=+1305166.722202760: ☑️ agreed by wjhuang2016.

[Benjamin2037]

/retest

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.5@62a0305). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-6.5     #47447   +/-   ##
================================================
  Coverage               ?   73.6477%           
================================================
  Files                  ?       1085           
  Lines                  ?     348930           
  Branches               ?          0           
================================================
  Hits                   ?     256979           
  Misses                 ?      75474           
  Partials               ?      16477