Stop serializaing hmr version state (#97146)
Mark VersionedContentMap as `serialization = "none"`
This will cause every dev session to start with an empty map, to ensure
_derived_ data from the old map doesn't survive, the functions
interacting with the state are all marked `session_dependent`.
This is directly motivated by the work on GC which runs into problems
with the State objects storing operations but not consistently
`connect`ing to them on cache hits, which causes the GC to drop them.
Additionally, this prevents eagerly recomputing all server hmr routes on
startup.
In theory this will slow down reconnecting a dev session, but the
underlying operations are still cached and the tasks computing Versions,
so it just the map that needs to be reconstructed, so the cost should be
minor. In fact i would guess that it is a bit faster to reconstruct this
map than to restore all the keys from disk in the case where the map is
large.
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