Allow insertion of transactions in the TxPool v2

[AurelienFT]

Currently, in the TxPool V2 you can only insert PoolTransaction. We need to instantiate the workflow to pass from Transaction to PoolTransaction. In fact it already exists in the transaction_conversion.rs file but it's a copy paste from the previous TxPool and used in tests only for now.

We want to change the behavior to verify in this order :

• Basic verification (max_gas, max_size, ...)
• Input verification (exists on pool or db if utxo_validation is asked)
• Verify predicate, wasm
• Include in the pool (which implies a new verification of the inputs)

@xgreenx can you confirm me the order ?

It will also be a great time to instantiate more tests and standardize them all.
Better type for the insert result in the pool

[xgreenx]

Yeah, the order it right=)

[xgreenx]

Done in #2263