Save the RLP decoded transaction in the storage of transaction pool instead of just transaction hash

[natanasow]

Problem

Currently, we're saving only the transaction hash in the transaction pool storage but for txpool_* related methods, we need the entire transaction object.

Solution

Save the RLP decoded transaction in the transaction pool.

Note

• We should use feat: Adds transaction pool funcitonality #4454 as a base till it's not merged.
• Affected classes: LocalPendingTransactionStorage and RedisPendingTransactionStorage.

Alternatives

No response