When testing a transaction for mempool acceptance, the fee must be calculated anyway. Thus, with minimal complexity overhead, the testmempoolaccept RPC could return the fee to the user.

#### Useful skills:

Basic understanding of the mempool, the Bitcoin Core RPC interface, and the functional test framework.

#### Want to work on this issue?

The purpose of the `good first issue` label is to highlight which issues are suitable for a new contributor without a deep understanding of the codebase.

You do not need to request permission to start working on this. You are encouraged to comment on the issue if you are planning to work on it. This will help other contributors monitor which issues are actively being addressed and is also an effective way to request assistance if and when you need it.

For guidance on contributing, please read [CONTRIBUTING.md](https://github.com/bitcoin/bitcoin/blob/master/CONTRIBUTING.md) before opening your pull request.

{
    RPCHelpMan{"decodescript",
                "\nDecode a hex-encoded script.\n",
                {
                    {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "the hex-encoded script"},
                },
                RPCResult{
                    RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::STR, "asm", "Script public key"},
                        {RPCResult::Type::STR, "type", "The output type (e.g. "+GetAllOutputTypes()+")"},
                        {RPCResult::Type::NUM, "reqSigs", "The required signatures"},
                        {RPCResult::Type::ARR, "addresses", "",
                        {
                            {RPCResult::Type::STR, "address", "bitcoin address"},
                        }},
                        {RPCResult::Type::STR, "p2sh", "address of P2SH script wrapping this redeem script (not returned if the script is already a P2SH)"},
                        {RPCResult::Type::OBJ, "segwit", "Result of a witness script public key wrapping this redeem script (not returned if the script is a P2SH or witness)",
                        {
                            {RPCResult::Type::STR, "asm", "String representation of the script public key"},
                            {RPCResult::Type::STR_HEX, "hex", "Hex string of the script public key"},
                            {RPCResult::Type::STR, "type", "The type of the script public key (e.g. witness_v0_keyhash or witness_v0_scripthash)"},
                            {RPCResult::Type::NUM, "reqSigs", "The required signatures (always 1)"},
                            {RPCResult::Type::ARR, "addresses", "(always length 1)",
                            {