Allocate hist_coords to max dimensions rather than arbitrary limit

[peverwhee]

What is the feature/what would you like to discuss?

In src/history/cam_history_support.F90, we have:

integer,          parameter         :: maxmdims        = 25  ! arbitrary limit
type(hist_coord_t),          public :: hist_coords(maxmdims)

Instead, as pointed out by @nusbaume in #274, we should determine the biggest number of dimensions that were needed (based on the user_nl_cam history variables configured), and have the maxmdims value set to that (with hist_coords then an allocatable variable that is allocated to that size)

Is there anyone in particular you want to be part of this conversation?

No response

Will this change (regression test) answers?

No

Will you be implementing this enhancement yourself?

Any Software Engineer can do this