community[minor]: Add UpstashRatelimitHandler (#21885)
Adding `UpstashRatelimitHandler` callback for rate limiting based on
number of chain invocations or LLM token usage.
For more details, see [upstash/ratelimit-py
repository](https://github.com/upstash/ratelimit-py) or the notebook
guide included in this PR.
Twitter handle: @cahidarda
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Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>
