Build the solution on Windows

[stuartmorgan]

Description

Switch from building Runner.vcxproj to Runner.sln on Windows, to allow
for multiple-project builds (e.g., separate plugin projects).

Related Issues

None

Tests

I added the following tests: None. Updated existing test.

Checklist

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• I updated/added relevant documentation (doc comments with ///).
• All existing and new tests are passing.
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Breaking Change

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• Yes, this is a breaking change (Please read Handling breaking changes). Replace this with a link to the e-mail where you asked for input on this proposed change.
• No, this is not a breaking change.

[jonahwilliams]

LGTM