[TxPool] Self pruning stuck transactions

[dbrajovic]

Description

This PR addresses the issue of valid "stuck" transactions. These transactions remain in the pool indefinitely due to being considered recoverable by consensus during block building.

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

Additional comments

Fixes EDGE-45

[zivkovicmilos]

Lookin' great 🚀

[Kourin1996]

Looks good to me

[DarianShawn]

Good to have this feature. 🙌

Just a little confused because of the method name TxPool.Drop().
DropAccountByTx() would make it more clearer?

[dbrajovic]

Good to have this feature. 🙌

Just a little confused because of the method name TxPool.Drop(). DropAccountByTx() would make it more clearer?

I do agree the naming is a bit unclear in the TxPool's API, but it was written that way for consistency. The only reason a transaction is needed as an argument is because address and nonce can be fetched from it.

In a future PR, this naming issue will get tackled.