Cleanup banking bench

[carllin]

Problem

Banking bench has certain portions that are hard to read

Summary of Changes

Refactor and cleanup

Fixes #

[carllin]

This didn't seem safe in the following scenario:

1. We create a new bank and add it to poh recorder:

   solana/banking-bench/src/main.rs

   Lines 418 to 428 in fc4e4b2

   	bank = bank_forks.working_bank();
   	insert_time.stop();
   	// set cost tracker limits to MAX so it will not filter out TXs
   	bank.write_cost_tracker().unwrap().set_limits(
   	std::u64::MAX,
   	std::u64::MAX,
   	std::u64::MAX,
   	);
   	poh_recorder.lock().unwrap().set_bank(&bank);

2. Before we can send the transactions for the next iteration, this bank is removed from poh recorder
3. We send the transactions for the next iteration, none of them land
4. check_txs returns because there's no bank:

   solana/banking-bench/src/main.rs

   Line 57 in fc4e4b2

   if poh_recorder.lock().unwrap().bank().is_none() {

5. No transactions were landed in this bank so txs_processed == bank.transaction_count()

[tao-stones]

I am almost sure I never see this assert fail for described scenario. I mean why would #2 happen?

[carllin]

I think it can happen if all the work after set_bank() takes longer than 350ms, things like the blockhash refresh, signature clearing, etc.

[codecov]

Codecov Report

Merging #24851 (fc4e4b2) into master (3155270) will increase coverage by 11.9%.
The diff coverage is 75.2%.

❗ Current head fc4e4b2 differs from pull request most recent head 73a5296. Consider uploading reports for the commit 73a5296 to get more accurate results

@@             Coverage Diff             @@
##           master   #24851       +/-   ##
===========================================
+ Coverage    70.0%    82.0%    +11.9%     
===========================================
  Files          36      596      +560     
  Lines        2255   165043   +162788     
  Branches      322        0      -322     
===========================================
+ Hits         1580   135439   +133859     
- Misses        560    29604    +29044     
+ Partials      115        0      -115     

[tao-stones]

nice clean up, lgtm! Not sure tho if necessary to disable assert!(txs_processed < bank.transaction_count());

Pull request has been modified.