Migrate raw Windows detection code to use the OSDetectionStrategy abstraction

[plaird]

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In BazelPathHelper and a few other locations we have code checking if we are running on Windows:

• BazelPathHelper

But this isn't good. We have an abstraction for that, to allow us to test on other platforms (ie. Windows) without running that platform.

• OSDetectionStrategy

Change the BazelPathHelper and other offenders to use the abstraction.