Proposal

This ticket coordinates open questions on further changes to 2.0 PRW spec while it's in an experimental stage. Best effort, we don't need to do all below to get to stable, but we could address/consider at least.

• Response Confirmation [PRW 2.0 spec] Sample Write Confirmation in Response #14359
• Double check if any change would be useful for Add proposal: Simplify joins with info metrics in PromQL proposals#37 cc @aknuds1
• Timestamp on exemplar is MUST @cstyan
• Anything for UTF-8? @ywwg