Fix for txpool loosing txs

[oliverbundalo]

Description

During proposal build a proposer removes txs from the accounts.promoted with accounts.promoted.pop. That leads to possible problem because those txs are permanently removed and in the case if that round fails the proposer can't take part in the consensus and further more there is a high possibility of nonce too high error for future proposals on that particular validator.

Changes include

• Bugfix (non-breaking change that solves an issue)
• Hotfix (change that solves an urgent issue, and requires immediate attention)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Checklist

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the relevant labels
• I have updated the official documentation
• I have added sufficient documentation in code

Testing

• I have tested this code with the official test suite
• I have tested this code manually

Manual tests

Run EOA load test in local.

[goran-ethernal]

Leaving some small comments, but in general LGTM.

[goran-ethernal]

Can we add some unit tests for this? It looks like it can be easily tested in various scenarios on the txpool and account level.

[oliverbundalo]

Can we add some unit tests for this? It looks like it can be easily tested in various scenarios on the txpool and account level.

Yes, 4 UTs have been added to txpool UTs

[Stefan-Ethernal]

Generally LGTM, left a couple of considerations.