fix(index): S3 EntityTooSmall error

[zhongzc]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

Set the buffer size for the OpenDAL writer to avoid uploading small parts.

Additionally, ensure that index-related exceptions cause panic in test scenarios.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR does not require documentation updates.

Refer to a related PR or issue link (optional)

[codecov]

Codecov Report

Attention: 39 lines in your changes are missing coverage. Please review.

Comparison is base (6320590) 85.81% compared to head (12ad0b6) 85.32%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3192      +/-   ##
==========================================
- Coverage   85.81%   85.32%   -0.49%     
==========================================
  Files         832      833       +1     
  Lines      136308   136802     +494     
==========================================
- Hits       116967   116726     -241     
- Misses      19341    20076     +735     

[killme2008]

LGTM

[zhongzc]

@evenyag @WenyXu PTAL