OpValueCache counted every re-delivery of an identical value as a new
source, but the proxy client is a single logical source that re-sends
values on push refresh or listen restart: the refcount grew unbounded
and expirations were never propagated. Add a countSources flag to
OpValueCache, OpCache and SearchCache; the proxy client disables it.
When a value is edited (same id, higher seq), only the reporting source
is known to hold the new version: replace it in place, reset the
refcount to 1 and emit a single add. Ignore older versions from lagging
sources on add, and ignore their expiration so they cannot release a
newer version still held by others.
ValueCache emits an edited value as an add instead of silently
refreshing its old copy, and applies a grace period of one type
expiration while the listen is synced so that a single lost refresh
notification does not drop a value the remote node still holds.
SearchCache::get only answers from the cache once the listen is synced,
so a get never returns a partial view that the network would complete.
Add the single-source OpCacheTester cases enabled by countSources.
Adrien Béraud