Document/promote GC Forms performance and load supported to alleviate client concerns

## Opportunity

Clients have been asking more about how GC Forms might be able to handle high volumes of traffic.
We might consider being more transparent / explicit about our confidence to support many users.

## Support tickets

https://cds-snc.freshdesk.com/a/tickets/29646
> Have you done any load testing that have results we could refer to?

https://cds-snc.freshdesk.com/a/tickets/29647
> Would GCForms be able to support a significant number of applicants submitting requests at the same time?

https://cds-snc.freshdesk.com/a/tickets/29968
> Will there be any technical limitation with GC Forms receiving hundreds of submissions around the same time? Could the server crash? What can we and your team do to mitigate any disruptions?

The issue names no files, tests, or entry points. Start by locating existing GC Forms performance or load-testing documentation and related deployment guidance; done means publishing verified capacity results and clear supported-volume guidance for clients.

Written by the indexing model from the issue text.