Add experimental support for sharding event persister. Again. (#8294)

This is *not* ready for production yet. Caveats:

1. We should write some tests...
2. The stream token that we use for events can get stalled at the minimum position of all writers. This means that new events may not be processed and e.g. sent down sync streams if a writer isn't writing or is slow.

1 files changed, 1 insertions, 0 deletions

diff --git a/changelog.d/8294.feature b/changelog.d/8294.feature
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+Add experimental support for sharding event persister.