Leverage fee as an anti-spam solution

### Is your feature request related to a problem?

Blockchains protocols usually leverage transaction's fees as a way to prevent failed transaction & spamming.
While it's true, in our current implementation, the transaction is not accepted if the pending transaction validation failed, causing resource consumption for the network for nothing.
The transaction's fee is not leveraged enough to incentivize good transactions.

### Describe the solution you'd like

The idea is to use to accept a transaction where the pending transaction check failed, and to flag it as `failed` using the Validation Stamp error flag.

**We might have to prevent a transaction to being validated if the previous signature is invalid; otherwise we could not guarantee the chain's integrity & ownership. In that case, it's an *invalid* transaction and not a *failed* transaction.**

So finally, a failed transaction will be replicated, and the fee will be consumed.

This will even become more useful when the smart contract recipient's code validation will be implemented to prevent invalid contract's transactions or violating a chain's conditions.

### Additional context

The UI might be adapted to print the invalid state of a transaction.

Epic: #306