refactor: replace info logs with debug logs in region server

[waynexia]

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Refer to a related PR or issue link (optional)

What's changed and what's your intention?

Tidy some logs in the region server

before	after
	Downgraded to debug log
	Downgraded to debug log. With a new info log to display region counter.
	Downgraded to debug log

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.08%. Comparing base (06e565d) to head (d03b2b3).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4829      +/-   ##
==========================================
- Coverage   84.33%   84.08%   -0.26%     
==========================================
  Files        1124     1124              
  Lines      204944   204946       +2     
==========================================
- Hits       172838   172321     -517     
- Misses      32106    32625     +519     

[fengjiachun]

LGTM