replay: include the timestamp in the traffic file names so that the files can be filtered by time

[djshow832]

What problem does this PR solve?

Issue Number: close #1069

Problem Summary:
We usually specify a start timestamp for replay. Currently, the traffic file names are in the format traffic-1.log. It's hard to locate the right file by a start timestamp.

What is changed and how it works:
Include the timestamp in the traffic file names, such as traffic-2025-09-10T17-01-56.073.log.

Check List

Tests

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

Notable changes

• Has configuration change
• Has HTTP API interfaces change
• Has tiproxyctl change
• Other user behavior changes

Release note

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

None

[djshow832]

/retest

[djshow832]

/retest

[codecov-commenter]

Codecov Report

❌ Patch coverage is 58.82353% with 21 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@f554cb5). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
pkg/sqlreplay/store/rotate.go	58.82%	12 Missing and 9 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1070   +/-   ##
=======================================
  Coverage        ?   67.47%           
=======================================
  Files           ?      140           
  Lines           ?    14455           
  Branches        ?        0           
=======================================
  Hits            ?     9753           
  Misses          ?     4031           
  Partials        ?      671           

Flag	Coverage Δ
unit	67.47% <58.82%> (?)

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[YangKeao]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: YangKeao

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-01-29 11:29:22.615701914 +0000 UTC m=+1270990.229658770: ☑️ agreed by YangKeao.