feat: cache logical region's metadata

[waynexia]

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?

Cache logical region's metadata to accelerate query.

Given some metrics are likely never to be used, this cache is loaded lazily.

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 87.07483% with 19 lines in your changes missing coverage. Please review.

Project coverage is 84.07%. Comparing base (aaa9b32) to head (fd18afe).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4827      +/-   ##
==========================================
- Coverage   84.37%   84.07%   -0.30%     
==========================================
  Files        1127     1124       -3     
  Lines      205164   204944     -220     
==========================================
- Hits       173104   172312     -792     
- Misses      32060    32632     +572     

[fengjiachun]

LGTM