Add TryGetOptionArgument

[SimonCropp]

So usages of TryGetOptionArgumentList are problematic

• some usages use the first arg and ignore the rest
• some usages check if there is only one and dont use the first if there is more than one
• some usages assume there is 1 and will throw if that is not correct

so this PR adds TryGetOptionArgument. which will formalize the usages. it will:

• return false if there is no arg
• return false if there is no items in the arg
• throw if there is more than 1

[Youssef1313]

I would return false only if TryGetOptionArgumentList returned false. Otherwise, throw if arguments.Length != 1, and I would probably throw Unreachable, since validation should have happened early and by the point we are calling this, we should be expecting us to be in a valid state.