Rate limiting is not updated until after the handler returns

[dgw]

Description

A long-running plugin callable with a rate limit can be called again in the same rate-limit context while it is still running. Metrics are not updated until after a Rule's handler completes, because the current metrics also need its exit code, but rate limiting is checked before dispatching the callable.

Reproduction steps

1. Build a long-running plugin callable ("dummy" way: time.sleep(10))
2. Give the callable a command, let's say .ratefail
3. Apply @plugin.rate(60) or whatever test value you like
4. Try to call .ratefail twice from a non-admin user (admins bypass rate limits)
5. Actual result: .ratefail will run twice

Expected behavior

.ratefail cannot be called twice because it is rate limited.

Environment

• Sopel .version: 7, 8-dev, probably earlier
• Sopel installed via: any method
• Python version: any supported
• Operating system: any supported

Notes

We discussed this on IRC today, and @Exirel already has a plan of attack. Therefore I've assigned the issue to him—but since we already thought there was an open issue about this when there actually wasn't, I thought it was a good idea to make one.