feat: retry failed transaction commit

[linguoxuan]

This commit implements the retry for transaction commits. It introduces a generic RetryRunner utility with exponential backoff and error-kind filtering, and integrates it into Transaction::Commit() to automatically refresh table metadata and retry on commit conflicts.

[wgtmac]

I've carefully reviewed the retry mechanism and found a few parity issues and a structural data-loss concern regarding how pending updates are held during retries. Please see the inline comments.

[wgtmac]

I just recall a design flaw in the interaction between PendingUpdate and Transaction and created a fix: #591. Without this fix, users have to cache all created pending update instances, otherwise they cannot retry them since they are weak_ptr in the transaction instance.

[wgtmac]

@linguoxuan Could you please rebase to resolve the conflict?

[wgtmac]

Thanks for the update and fixing the CI! I've just reviewed it for a quick pass.

[wgtmac]

Is this ready to review again?

[linguoxuan]

Is this ready to review again?

Yes. PTAL.