QoL Improvements to Campaign 'Add Leads Via CSV'

Increase the lead limit per upload from 500 to a minimum of 1000 - this will reduce the time it takes to import leads by 50%.

Auto-map required fields - based on matching column headers, this will reduce the error rate on mismatching required fields.

When mapping fields, change the default value from “Ignore Field” to “Custom Field” - assume that we are using a template and that all fields are intentional, this will save dozens of extra clicks and significantly speed up imports.