maps: evaluate splitting info metric out into separate metrics

[anitgandhi]

things are like max_entries, value_size, key_size, etc are likely more valuable as individual gauges as opposed to all being labels in a single info metric.
for example, being able to do 100 * (ebpf_map_entries / ebpf_map_max_entries) in a grafana visualization to see the percentage utilization of a given map, based on the map_id. Then, that map_id can be joined against map_info to get the name, for convenience.