feat: Add Zep Cloud community components, update docs and examples

[paul-paliychuk]

We have recently released our new zep-cloud sdks that are compatible with Zep Cloud (not Zep Open Source).

We have also maintained our Cloud version of langchain components (ChatMessageHistory, VectorStore) as part of our sdks.

This PRs goal is to port these components to langchain community repo, and close the gap with the existing Zep Open Source components already present in community repo (added ZepCloudMemory,ZepCloudVectorStore,ZepCloudRetriever). Also added a ZepCloudChatMessageHistory components together with some expression language examples ported from our repo.

Also includes the documentation update - added pages for Zep Cloud components.

We have left the original open source components intact on purpose as to not introduce any breaking changes.

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Name	Status	Preview	Comments	Updated (UTC)
langchainjs-api-refs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 21, 2024 6:01pm
langchainjs-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 21, 2024 6:01pm

[jacoblee93]

Thanks for waiting! Please also run yarn format.

[paul-paliychuk]

@jacoblee93 my bad, just ran the formatter

[jacoblee93]

Thank you! Couldn't push to your branch, so pushed updates here: #5542

[jacoblee93]

Closed in favor of #5542