Re-export the ResourceUsage structs in drivers package to avoid drivers
directly depending on the internal client/structs package directly.
I attempted moving the structs to drivers, but that caused some import
cycles that was a bit hard to disentagle. Alternatively, I added an
alias here that's sufficient for our purposes of avoiding external
drivers depend on internal packages, while allowing us to restructure
packages in future without breaking source compatibility.
this allows us to drop a cyclical import, but is subobptimal as it
requires BaseDriver tests to move. This falls firmly into the realm of
being a hack. Alternatives welcome.
