feat: add cursor statements

[sunng87]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

This patch is to address #5077

What's changed and what's your intention?

In this patch, I added initial support for postgres cursor related statements:

• DECLARE $cursor CURSOR FOR $query
• FETCH $size FROM $cursor
• CLOSE $cursor

This patch, together with #5081 , will hopefully enable us as a postgresql foreign data wrapper compatible server.

Some utility functions are added to recordbatch module, allows to slice and merge recordbatch(es).

Tests to be added.

Checklist

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

[coderabbitai]

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[codecov]

Codecov Report

Attention: Patch coverage is 96.08939% with 14 lines in your changes missing coverage. Please review.

Project coverage is 83.81%. Comparing base (5bdea1a) to head (55c0aa6).
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5094      +/-   ##
==========================================
- Coverage   84.04%   83.81%   -0.23%     
==========================================
  Files        1157     1166       +9     
  Lines      216477   217098     +621     
==========================================
+ Hits       181944   181968      +24     
- Misses      34533    35130     +597     

[killme2008]

LGTM