When `IgnoreUnknownArguments` is true, do not assume any single-dash argument matches a correlating short character option

[joeyj]

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Currently, Tokenizer will assume a match for a short option when it encounters a single-dash argument, when the first character matches. This is unexpected when IgnoreUnknownArguments is set to true--since it should ignore unknown arguments.

https://github.com/commandlineparser/commandline/blob/b0b0ec9f5470bacc0823c013a599ba3b4e115900/src/CommandLine/Core/Tokenizer.cs#L172-L183