resourceloader: Include lessVars in FileModule definition summary

resourceloader: Include lessVars in FileModule definition summary

This already worked as expected for any module that uses the new
enableModuleContentVersion model, but for the majority of file modules
this is not yet the case for performance reasons. As such, make
sure lessVars are included in our manual tracking.

Include it conditionally to avoid changing the array for other modules,
which would needlessly invalidate their cache.

Bug: T171809
Change-Id: Ib250068e0ecfc29a09ca33c23bef901ee0482bf2