Modules: Make imported targets fall back to `Release`

Find modules only detect Debug and Release configurations.  All other
configurations will fall back to the configuration listed as the first
entry in `IMPORTED_CONFIGURATIONS`.  Switch the order so that `Release`
is listed first, as this is a better fallback than `Debug` for the
`RelWithDebInfo` and `MinSizeRel` configurations.  See issue #16091.

This approach is recommended by documentation in `cmake-developer(7)`
added by commit v3.2.0-rc1~286^2~1 (Help: Document IMPORTED_CONFIGURATIONS
target property for Find modules, 2014-12-04).