Add an alert for ourselves when getting close to our AWS limit

[ecayer]

• Add an alert(s) for when we approach our max spend limit for SMS in the future - note that this can only be done in the Commercial account, which we use for staging, so this could be difficult with our current setup (the recommendation is to just not use the Commercial account for any actual workloads when there's a GovCloud account associated with it...)
• Request an increase for another max spend limit when we have a better idea of how much we should