Aimed at fixing: https://github.com/tendermint/tendermint/actions/runs/3598326181/jobs/6060978982

The issue is that if the context in the createBatch function is canceled before all of the transactions are generated, we will hit the return in the ctx.Done() case of the select and the wg.Done() will never be called, causing the createBatch function to never return and therefore never allow more transactions to be generated.

To test this, I passed a context with very short timeout into the createBatch function and observed that, after the initial set of transactions fail because the connection is not yet established to the node, the ctx.Done() case is hit and no more transactions are ever created, leading to the same failure we see in the e2e nightly.

A sample of output from this experiment is below:

I[2022-12-02|09:43:02.357] Removing Docker containers and networks
I[2022-12-02|09:43:04.122] cleanup dir                                  msg="Removing testnet directory \"networks/nightly/gen-0000\""
I[2022-12-02|09:43:06.128] setup                                        msg="Generating testnet files in \"networks/nightly/gen-0000\""
I[2022-12-02|09:43:06.137] Starting initial network nodes...
I[2022-12-02|09:43:06.137] load                                         msg="Starting transaction load (16 workers)..."
broadcast fail
broadcast fail
...
broadcast fail
ctx done
broadcast fail
ctx done
ctx done
... 
ctx done

I[2022-12-02|09:43:08.785] start                                        msg="Node validator01 up on http://127.0.0.1:5701"
I[2022-12-02|09:43:08.785] Waiting for initial height                   height=1 nodes=1 pending=0
I[2022-12-02|09:43:10.788] wait until                                   msg="Waiting for all nodes to reach height 6..."
I[2022-12-02|09:43:15.014] Injecting evidence through validator01 (amount: 1)...
I[2022-12-02|09:43:18.036] Finished sending evidence (height 8)
I[2022-12-02|09:43:18.039] wait until                                   msg="Waiting for all nodes to reach height 14..."
E[2022-12-02|09:43:23.173] Transaction load failed: failed to submit any transactions
E[2022-12-02|09:43:23.173] failed to submit any transactions

This pull request also contains a fix to the number of transactions generated per batch. The purpose of the LoadTxBatchSize parameter was to generate a total of LoadTxBatchSize tx each second. However, the code as written generates workerPoolSize * LoadTxBatchSize transactions since each worker creates LoadTxBatchSize. This pull request places another loop outside the worker pool that instructs the worker pools to generate new transactions for a total of LoadTxBatchSize.

A full nightly run of the e2e test has been run with this code in place: https://github.com/tendermint/tendermint/actions/runs/3602704988

PR checklist

• Tests written/updated, or no tests needed
• CHANGELOG_PENDING.md updated, or no changelog entry needed
• Updated relevant documentation (docs/) and code comments, or no
  documentation updates needed