Cloudflare worker sub-sentries

[Ivshti]

To increase scalability, we can offload limits checking (services/sentry/lib/access) to a cloudflare worker

Instead of redis, we will use Cloudflare Workers KV

The worker will work in the following way:

• load (cached) the .spec.eventSubmission of the channel
• apply some of the the logic in access:
  • if we're not providing auth and there are limits, apply them; if we're authorized to post the event(s), then forward them to the Sentry, using a special auth token generated for this worker (so the Sentry doesn't have to check the limits again)
  • in any other case (auth provided or no limits), just proxy the request

This has the following benefits:

• the Sentry will not have to do the work of checking limits
• we reduce the traffic to the Sentry

[Ivshti]

performance is sufficient for now; will be improved greatly by the Rust implementation too