feat(websocket_server sink): add ACK support for message buffering

[esensar]

Summary

This adds ACK support for message buffering, allowing this component to cache latest received messages for all clients, as an alternative to clients sending that in a query parameter.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

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Sponsored by Quad9

[esensar]

I still need to add tests here, do more detailed testing and add documentation.