Reapply PR#31: optimize retry pool

[KirillLykov]

Problem

Transactions not included in the retry pool on full utilization

This PRs adds back #31

Summary of Changes

• do not insert transactions with zero max_retries to the retry pool
• remove transactions reached max_retries in the same iteration of the loop
• dynamically select sleep time between iterations based on last_sent_time in TransactionInfo

[mergify]

Backports to the beta branch are to be avoided unless absolutely necessary for fixing bugs, security issues, and perf regressions. Changes intended for backport should be structured such that a minimum effective diff can be committed separately from any refactoring, plumbing, cleanup, etc that are not strictly necessary to achieve the goal. Any of the latter should go only into master and ride the normal stabilization schedule. Exceptions include CI/metrics changes, CLI improvements and documentation updates on a case by case basis.