Bugfix for Update cmdlet attempting to reinstall latest preview version

[anamnavi]

PR Summary

Fix bug related to updating a prerelease version package. If the package has latest prerelease version, the discrepancy with System.Version and NuGetVersion instances used for latest version comparison was causing the latest preview version to be attempted to be reinstalled. With this fix it can detect correctly if it the latest version is the latest and not reinstall.

PR Context

Resolves #464 #818 #749 #619

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[alyssa1303]

This might also fix this issue too #749