perf: eliminate hot-path allocations and fix double-lock race in sync structures

[Copilot]

Several hot-path code paths had unnecessary heap allocations and a correctness issue in SyncMapImpl.removeIf. This PR addresses the most impactful ones.

Changes

AtomicBoolean removed from stream message handler (both caches)

processStreamMessage runs on every Redis stream event. It was allocating a fresh AtomicBoolean solely to smuggle a flag out of the getAndUpdate lambda. Replaced with arithmetic on the returned prevVersion:

// Before
val shouldInvalidate = AtomicBoolean(false)
val oldVersion = lastVersion.getAndUpdate { cur ->
    if (...) { shouldInvalidate.set(true); version } else cur
}
if (shouldInvalidate.get()) { … }

// After
val prevVersion = lastVersion.getAndUpdate { cur -> … }
if (prevVersion != 0L && version > prevVersion + 1) { … }

SyncMapImpl.removeIf — two write locks collapsed to one

The original code held the write lock to collect matching keys, released it, then re-acquired it to remove them. This left a mutation window between the two critical sections and contained a bug: removeManyRemote was called with all matched keys, not just the ones actually removed in the second pass. Now uses a single fastIterator().remove() pass with parallel ObjectArrayLists (no Pair boxing):

lock.write {
    val it = map.object2ObjectEntrySet().fastIterator()
    while (it.hasNext()) {
        val e = it.next()
        if (predicate(e.key, e.value)) {
            removedKeys.add(e.key); removedVals.add(e.value); it.remove()
        }
    }
}
removeManyRemote(removedKeys) // only actually-removed keys

overrideFromRemote intermediate collections eliminated

• SyncMapImpl: map { }.toMap() (produces List<Pair> + LinkedHashMap) → single loop into a pre-sized Object2ObjectOpenHashMap.
• SyncSetImpl / SyncListImpl: map(::decodeValue) + addAll → mapTo directly into the target collection, skipping the intermediate list.

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