Extend data types support for parsers

[MCarlomagno]

The trait IntoScVal performs parsing between rust native types and ScVal (Soroban types format in the client library).

Currently the trait supports most common data types used for soroban contracts, but there are a couple missing, we want to create new parsers, extending the support to any Soroban ScVal type:

pub enum ScValType {
    // already supported
    Bool = 0,
    U32 = 3,
    I32 = 4,
    U64 = 5,
    I64 = 6,
    Duration = 8,
    Bytes = 13,
    String = 14,
    Vec = 16,
    Address = 18,

    // not supported
    Void = 1,
    Error = 2,
    Symbol = 15,
    Timepoint = 7,
    Map = 17,
    U128 = 9,
    I128 = 10,
    U256 = 11,
    I256 = 12,
    ContractInstance = 19,
    LedgerKeyContractInstance = 20,
    LedgerKeyNonce = 21,
}