Support evm compatible accounts using private key directly

[kpachhai]

the params for hedera network currently is:

params: {
   externalAccount: true,
   accountId: "0.0.45345"
}

the params for evm networks could be:

params: {
   externalAccount: true,
   evmAddress: "0xdasdfasdf"
}

or think of a better solution to how the params should look like: something like:

params: {
   externalAccount: 'hedera',
   externalData: {
        accountId: "0.0.45345"
    }
}

for evm, it could be :

params: {
   externalAccount: 'evm',
   externalData: {
        address: "0xdasdfasdf"
    }
}

for bitcoin, it could be: for evm, it could be :

params: {
   externalAccount: 'bitcoin',
   externalData: {
        address: "basdfasasdfasdf"
    }
}

Figure out the best modular solution that can work with any blockchain networks in the future we decide to support.