Fix systemversion("latest") on VS2017

[starkos]

What does this PR do?

My take on a cleaned-up version of #1317. Implements the workaround described here to enable VS 2017 to discover the correct version of the Windows 10 SDK.

h/t to @jeaiii to discovering the fix, and putting together the original PR.

How does this PR change Premake's behavior?

Should not be any breaking changes. Does add this markup to every VS 2017 project, regardless of whether systemversion("latest") is used or not:

<LatestTargetPlatformVersion>$([Microsoft.Build.Utilities.ToolLocationHelper]::GetLatestSDKTargetPlatformVersion('Windows', '10.0'))</LatestTargetPlatformVersion>

The alternative is to scan through all of the project configurations to see if the value has been set or not before writing, but the markup is ignored if not used, and querying all of the configurations can be relatively expensive. If no one complains, this is a more efficient approach.

Anything else we should know?

No.

Did you check all the boxes?

• Focus on a single fix or feature; remove any unrelated formatting or code changes
• Add unit tests showing fix or feature works; all tests pass
• Mention any related issues N/A
• Follow our coding conventions
• Minimize the number of commits

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