feat: max-txn-ops option

[fengjiachun]

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 max_txn_ops option for metasrv. If using etcd as the store, this value should be less than or equal to the --max-txn-ops option value of etcd. If using another store, this option can be ignored.

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.

[codecov]

Codecov Report

Attention: Patch coverage is 87.14286% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 85.02%. Comparing base (a218f12) to head (7688270).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3458      +/-   ##
==========================================
- Coverage   85.42%   85.02%   -0.41%     
==========================================
  Files         896      896              
  Lines      147137   147236      +99     
==========================================
- Hits       125696   125190     -506     
- Misses      21441    22046     +605     

[tisonkun]

Generally LGTM.

[waynexia]

LGTM