feat: add open candidate region step

[WenyXu]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

This step opens the candidate region on to_peer.

Behaviors:

Abort(non-retry):

• Table Info is not found.
• The Datanode is unreachable(e.g., Candidate pusher is not found).
• Unexpected instruction reply.
• Another procedure is opening the candidate region.

Retry:

• Exceeded deadline of open instruction.
• Datanode failed to open the candidate region.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.

Refer to a related PR or issue link (optional)

#2700
Waits for #2756

[codecov]

Codecov Report

Merging #2757 (028339a) into develop (3ab4947) will decrease coverage by 0.30%.
Report is 1 commits behind head on develop.
The diff coverage is 96.11%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2757      +/-   ##
===========================================
- Coverage    85.36%   85.07%   -0.30%     
===========================================
  Files          777      777              
  Lines       126187   126906     +719     
===========================================
+ Hits        107718   107960     +242     
- Misses       18469    18946     +477