chore: add logs for setting the region to writable

[WenyXu]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

What's changed and what's your intention?

add logs for setting the region to writable

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

Attention: Patch coverage is 66.66667% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 85.13%. Comparing base (5df3d4e) to head (4a3376c).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4044      +/-   ##
==========================================
- Coverage   85.42%   85.13%   -0.30%     
==========================================
  Files         983      983              
  Lines      170493   170510      +17     
==========================================
- Hits       145652   145158     -494     
- Misses      24841    25352     +511     

[waynexia]

Others LGTM

[evenyag]

LGTM