[Maps] unable to edit cluster vector styles styled by count when switching to super fine grid resolution

[nreese]

Steps to view issue:

1. Add clusters layer to map
2. Change "Grid resolution" to "super fine"
3. Try to set "Symbol size" style. Notice how "By value" select is disable and there are no fields available for by value.

We had a similar issue, #70601, that occurred when removing fields. This was resolved by converting dynamic styles to static styles when there are no next fields in #70621.

The problem is that the field still exists, it just gets removed from the field select list. The logic in getDescriptorWithMissingStylePropsRemoved needs to be updated to be smarter and account for this field list filtering.

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)