(from discussion on IRC. Currently a global `settxfee` has to be changed to override the fee rate, it would make sense to be able to specify it on a per-transaction basis. This would continue #7518)

```
-*- jonasschnelli thinks we should probably add a optional feerate parameter to fundrawtransaction
<wumpus> jonasschnelli: there isn't one yet?
-*- jonasschnelli looking..
<wumpus> I'm surprised, would be so much better than changing a global
<jonasschnelli> no.. i don't think so. Maybe there is a PR.
<sipa> there is a pr
<jonasschnelli> Hard to keep track of everything. :)
<wumpus> no, the PR does it wrong
```

Regarding implementation:

```
<jonasschnelli> The ugly thing is, that CreateTransaction uses the static DEFAULT_TARGET
<wumpus> passing in an optional feerate would be the obvious thing to do
<jonasschnelli> So, this would require some refactoring.
<sipa> just add a confirmation target to coincontrol
<jonasschnelli> Yes. This sounds good.
<wumpus> right, just slap it into coincontrol
<sipa> wasn't there a PR that added a bunch of options to fundrawtransaction?
<sipa> including that
<jonasschnelli> Not the feerate.
<jonasschnelli> But the rest is merged.
```

const vector<unsigned char> &vchCryptedSecret)
{
    if (!CCryptoKeyStore::AddCryptedKey(vchPubKey, vchCryptedSecret))
        return false;
    if (!fFileBacked)
        return true;
    {
        LOCK(cs_wallet);
        if (pwalletdbEncryption)
            return pwalletdbEncryption->WriteCryptedKey(vchPubKey,
                                                        vchCryptedSecret,
                                                        mapKeyMetadata[vchPubKey.GetID()]);
        else
            return CWalletDB(strWalletFile).WriteCryptedKey(vchPubKey,
                                                            vchCryptedSecret,
                                                            mapKeyMetadata[vchPubKey.GetID()]);
    }
    return false;
}
bool CWallet::LoadKeyMetadata(const CPubKey &pubkey, const CKeyMetadata &meta)
{
    AssertLockHeld(cs_wallet); 
    if (meta.nCreateTime && (!nTimeFirstKey || meta.nCreateTime < nTimeFirstKey))
        nTimeFirstKey = meta.nCreateTime;
    mapKeyMetadata[pubkey.GetID()] = meta;
    return true;
}
bool CWallet::LoadCryptedKey(const CPubKey &vchPubKey, const std::vector<unsigned char> &vchCryptedSecret)