Take a pass over all mongostream metrics to see if there are any metrics that can use kProcessorIdLabelKey label. This would allow us to use processor_id variable for more of the panels on SPP Overview Grafana dash.

Make sure this change does not blow up the number of time series mongostream generates: https://victoria-metrics.corp.mongodb.com/select/0/vmui/#/cardinality?date=2024-04-08&match=%7Bnamespace%3D%22streams-prod%22%2C+__name__%3D%7E%22.*mstream.*%22%7D&topN=300&focusLabel=