Make it easier for me to discover I'm being throttled

## Summary

Account throttling can manifest to a user as lack of events, which can also be caused by misconfiguration. We should make it clearer when throttling is the cause of lack of events.

## Motivation

User reports [in Discord](https://discord.com/channels/621778831602221064/804769373025075301/829063782033522779) that it took them longer than was awesome to discover that their account was being throttled:

> Is there an issue with Sentry's API currently?
> Im not getting errors to report to sentry.
> This staging environment has been in staging(production) for nearly a year without issues, no dependencies have been updated, or critical changes to sentry.
>> there are no known issues.
>
> ty
> How would I Identify if my account is being throttled due to errors being reported?
>> all the information should be in Stats in the sidebar
>
> Would there be a clear indicator if my account has been restricted?
> I think im getting into to many transactions for the 'free' account.
>> you also get email notifications if I recall
>
> who checks that :smile:
> id recommend a friendly msg that posts at top of page on error issues reporting page when youve exhausted your limits to give a better QOL experience so users dont go thru unneeded debugging thinking theres something wrong with their environment.
and directing them to the billing/subscription upgrade page.