Capture values across multiple .upToNextOption option uses

[natecook1000]

This fixes a bug where an @Option array defined with the .upToNextOption parsing strategy would only capture the last "group" of elements. e.g. in:

example --test one two --test three four

the --test property would only have the value ["three", "four"].

Fixes rdar://73908471

Checklist

• I've added at least one test that validates that my change is working, if appropriate
• I've followed the code style of the rest of the project
• I've read the Contribution Guidelines
• I've updated the documentation if necessary

[natecook1000]

Note, this isn't source breaking, but changes the behavior of existing CLI tools. For options defined like @Option(parsing: .upToNextOption) var names: [String] = [], the following is no longer a valid use of the command:

$ example --names --other-flag

[natecook1000]

@swift-ci Please test