[Issue #3588] Add New Relic license key env var (#3592)

## Summary
Fixes #3588 

### Time to review: __2 mins__

## Changes proposed
Add env var for a New Relic license key

Also updated parameter store to have that key

## Context for reviewers
Pretty simple env var update - I did verify the key I grabbed works and
you can actually see some local metrics in New Relic.

infra/api/app-config/env-config/environment-variables.tf

@@ -38,6 +38,11 @@ locals {
       secret_store_name = "/api/${var.environment}/api-auth-token"
     }
 
+    NEW_RELIC_LICENSE_KEY = {
+      manage_method     = "manual"
+      secret_store_name = "/api/${var.environment}/new-relic-license-key"
+    }
+
     LOGIN_GOV_CLIENT_ASSERTION_PRIVATE_KEY = {
       manage_method     = "manual"
       secret_store_name = "/api/${var.environment}/login-gov-client-assertion-private-key"