Adds Brotli compression for FsCodec.SystemTextJson, with support for conditionally compressing based on the EventType
Equinox.DynamoStore externalized compression and encoding from the outset via the FsCodec.Compression helpers in FsCodec.Box (which remain for full binary backcompat with 3.x, but are Obsoleted). These helpers now move into FsCodec as FsCodec.Encoding, with some minor renaming and polish.
These generalizations allow that same scheme to be applied in conjunction with Equinox.CosmosStore v 4.1.0 and later (which no longer duplicates this functionality internally as versions prior to that did)