winemac has functions+structs to enumerate "adapters", "monitors", and "displays", but these are all reporting the same underlying objects (macOS screens/displays) in slightly different ways.
"displays" is the oldest one, and the least connected to the current win32u concepts of sources and monitors.
To remove `macdrv_display`, I essentially integrated `macdrv_get_displays()` into `macdrv_get_monitors()` (where it was used to get `RcMonitor` and `RcWork`). I converted one other caller to use `macdrv_get_monitors()` instead, and the other callers didn't actually support multiple monitors anyway.
I may work on eliminating the redundancy between "adapters" and "monitors" in the future, as far as I can tell "monitors" are a superset of "adapters" (monitors includes mirrors, adapters does not).