Add “Leads (Form)” (Instant Form results) metric for Meta Ads#1535

Please add a dedicated Meta Ads metric to match Ads Manager Results = “Leads (Form)” (leads generated via Instant Forms / on-Facebook lead forms). Current “Leads” and “On-Facebook Leads” fields don’t always match the Results: Leads (Form) column for some accounts, so we need a separate field that reproduces the Ads Manager value exactly for reporting