[essimaging] `maximum_resolution_achievable` should not hardcode "time" as the "third" dimension

[jokasimr]

Currently one of the arguments to maximum_resolution_achievable function (https://scipp.github.io/essimaging/generated/modules/ess.imaging.tools.resolution.maximum_resolution_achievable.html#ess.imaging.tools.resolution.maximum_resolution_achievable) is the bin-edges of the time coordinate.

This is not very flexible, sometimes the third coordinate is wavelength or event_time_offset or maybe something different.

To fix this we should rename the argument and update the documentation, and maybe the implementation, to make it clear the third argument can be a non-time dimension.