PERFORMANCE: Lucene.Net.Replicator.LocalReplicator::CheckExpiredSessions(): Remove unnecessary dictionary allocation

[NightOwl888]

Is there an existing issue for this?

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Task description

In Lucene.Net.Replicator.LocalReplicator::CheckExpiredSessions(), there is an extra .ToArray() call that allocates a new collection to iterate the Values:

lucenenet/src/Lucene.Net.Replicator/LocalReplicator.cs

Lines 135 to 146 in a739a80

	private readonly IDictionary<string, ReplicationSession> sessions = new Dictionary<string, ReplicationSession>();
	/// <exception cref="InvalidOperationException"></exception>
	private void CheckExpiredSessions()
	{
	// .NET NOTE: .ToArray() so we don't modify a collection we are enumerating...
	// I am wondering if it would be overall more practical to switch to a concurrent dictionary...
	foreach (ReplicationSession token in sessions.Values.Where(token => token.IsExpired(ExpirationThreshold)).ToArray())
	{
	ReleaseSession(token.Session.Id);
	}
	}

J2N 2.1 includes the update to J2N.Collections.Generic.Dictionary<TKey, TValue> that allows deleting while iterating forward through the collection in older target frameworks. So, swapping the implementation of the sessions field will allow us to remove this extra allocation.