refactor(package_info_plus): use win32's built-in structs and helpers

[halildurmus]

Description

Replaces the custom FILEATTRIBUTEDATA struct and fileTimeToDartDateTime helper with WIN32_FILE_ATTRIBUTE_DATA and FILETIME.toDateTime() already provided by package:win32, removing duplicated logic and reducing maintenance overhead.

Also fixes the URLs for the reference files in file_version_info.dart.

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I titled the PR using Conventional Commits.
• I did not modify the CHANGELOG.md nor the plugin version in pubspec.yaml files.
• All existing and new tests are passing.
• The analyzer (flutter analyze) does not report any problems on my PR.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate that with a ! in the title as explained in Conventional Commits).
• No, this is not a breaking change.