*: change some log level from info to debug

[djshow832]

What problem does this PR solve?

Issue Number: close #462

Problem Summary:
There are too many logs, e.g. new connection, close connection, begin redirect connection, redirect succeeds.

What is changed and how it works:
Change some log level from info to debug

Check List

Tests

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

Connect to TiProxy and check logs.

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.

Change the log level of some logs from info to debug

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: xhebox

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• OWNERS [xhebox]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-01-25 03:33:22.293511623 +0000 UTC m=+1018043.857809328: ☑️ agreed by xhebox.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

❗ No coverage uploaded for pull request base (main@837db0b). Click here to learn what that means.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #463   +/-   ##
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  Coverage        ?   63.89%           
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  Files           ?       61           
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  Branches        ?        0           
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  Hits            ?     3649           
  Misses          ?     1771           
  Partials        ?      291           

Flag	Coverage Δ
unit	63.89% <0.00%> (?)

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