Update Artillery with projected production load

[coilysiren]

Summary

https://github.com/HHS/simpler-grants-gov/issues/2322

• < API gateway scales to massive quantities by default >
• update frontend as needed (unlikely)
• update API as needed (likely)
• update database as needed (likely)
• update opensearch as need (unlikely)

Acceptance criteria

Artillery configuration updated

[coilysiren]

Artillery scales up to the projected number immediately, but what we actually want is a smooth scale up

example: start from 100 users / (minute?) up to 10k users / (minute?) slowly

ramp up rate: https://www.artillery.io/docs/reference/test-script#ramp-up-rate

is it per minute? per hour? concurrently? we should find that out

do we have the number for production grants.gov ?