Optimize block start time

[huangminghuang]

This PR optimizes the start times for block producing. Before this PR, a producer always starts producing each block at the time point of the multiple of config::block_interval_us (i.e. 500 ms) and spend at most cpu-effort-percent (i.e. 80 by default, so it is 400 ms out of 500 ms) to produce each block. Therefore it leaves 100 ms idle time in between each block producing. In this PR, we leave no gap in between block producing so that the last block in each production round can reach the next producer earlier so that the next producer can start producing on schedule.

Removed configuration options:

• produce-time-offset-us
• last-block-time
• last-block-cpu-percent

The schema for Runtime_Options has changed to

struct runtime_options {
      std::optional<int32_t>   max_transaction_time;
      std::optional<int32_t>   max_irreversible_block_age;
      std::optional<int32_t>   cpu_effort_us;
      std::optional<int32_t>   max_scheduled_transaction_time_per_block_ms;
      std::optional<int32_t>   subjective_cpu_leeway_us;
      std::optional<double>    incoming_defer_ratio;
      std::optional<uint32_t>  greylist_limit;
   };

Resolves #726

[spoonincode]

should this have been add_test()ed?

[huangminghuang]

fixed by 6ee7e1f

[heifner]

info 2023-03-23T14:06:34.304 nodeos producer_plugin.cpp:2700 produce_block ] Produced block ccc88fbdd3f57610... #155 @ 2023-03-23T14:06:35.500 signed by defproducerc [trxs: 0, lib: 95, confirmed: 0, net: 0, cpu: 100, elapsed: 145, time: 4841]
This is the 12th block of the round. It is produced ~1.2 seconds early as expected by default 80% cpu-effort. The first block of the round was produced ~100ms early as expected.