infosync: move server info sync part of structs out to a separate pkg

[D3Hunter]

What problem does this PR solve?

Issue Number: ref #61702

Problem Summary:

What changed and how does it work?

for cross keyspace of nextgen, we need to sync the info schema too for system tables, so we need to register the instance which is accessing cross keyspace session as a separate virtual server, so we will abstract the server info sync part out of info sync to make it standalone

in this PR, we only move some struct and constant, as the change is quite large, so file a separate PR.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test ONLY MOVE AND RENAME STRUCTS, NO LOGIC CHANGE

  • 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

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[D3Hunter]

rename those structs won't affect json marshal, https://pkg.go.dev/encoding/json

Embedded struct fields are usually marshaled as if their inner exported fields were fields in the outer struct,

[codecov]

Codecov Report

Attention: Patch coverage is 81.10236% with 24 lines in your changes missing coverage. Please review.

Project coverage is 74.8534%. Comparing base (b40975c) to head (d44b6d6).
Report is 14 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #62609        +/-   ##
================================================
+ Coverage   72.8645%   74.8534%   +1.9888%     
================================================
  Files          1767       1814        +47     
  Lines        485973     494723      +8750     
================================================
+ Hits         354102     370317     +16215     
+ Misses       110217     101280      -8937     
- Partials      21654      23126      +1472     

Flag	Coverage Δ
integration	48.8058% <12.5984%> (?)
unit	72.1996% <81.1023%> (+0.0507%)	⬆️

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Components	Coverage Δ
dumpling	52.7804% <ø> (ø)
parser	∅ <ø> (∅)
br	63.1541% <ø> (+16.8519%)	⬆️

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[D3Hunter]

/retest

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-07-25 03:27:56.921065098 +0000 UTC m=+133193.655081678: ☑️ agreed by joechenrh.
• 2025-07-25 05:48:27.756712314 +0000 UTC m=+141624.490728904: ☑️ agreed by GMHDBJD.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: GMHDBJD, hawkingrei, joechenrh

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