Review and remove IDerivativeSecurity from Future

[Martin-Molinero]

Expected Behavior

• Future interface is accurate

Actual Behavior

• Security Future.Underlying is always null and doesn't seem to have a reason for existance. See https://github.com/QuantConnect/Lean/pull/4804/files#r499031629

Potential Solution

• Remove Future.Underlying and IDerivativeSecurity from Future

Reproducing the Problem

N/A

System Information

N/A

Checklist

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• I have confirmed that this issue exists on the current master branch
• I have confirmed that this is not a duplicate issue by searching issues

• I have provided detailed steps to reproduce the issue