Task #1907952

Purpose
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The number of generated leads/opportunities from the mass mailing on the stat button should count
both active and archived leads/opportunities.

The stat buttons on mass mailing added by sales and crm apps should appear on every selected 'model'
for the recipients (a mass mailing sent to 'leads' can generate sales).

Specs
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Opportunity stat button:
- double check that the number is based on both leads or opportunities, active or archived

Stat buttons Leads #, Quotations #, Invoice Amount should appear on the form all the time for showcase purposes

closes odoo/odoo#29568