Tests: enable windows remote builder tests

[iankingori]

Description

Remote builder tests do not currently run any validation for windows scenarios.

I'm adding this issue to track adding a windows remote builder to the test suite and enable windows platform tests.

This is a follow up to this PR adding npipe support to buildx. With experimental support for buildkitd (WCOW) on windows out, there's a lot more work to enable additional builder drivers for Windows and improving state of CI should help catch regressions