Update RELEASE_NOTES.md for 1.5.0-alpha3 release

[Arkatufus]

1.5.0-alpha3 November 15th 2022

Akka.NET v1.5.0-alpha3 is a security patch for Akka.NET v1.5.0-alpha2 but also includes some other fixes.

Security Advisory: Akka.NET v1.5.0-alpha2 and earlier depend on an old System.Configuration.ConfigurationManager version 4.7.0 which transitively depends on System.Common.Drawing v4.7.0. The System.Common.Drawing v4.7.0 is affected by a remote code execution vulnerability GHSA-ghhp-997w-qr28.

We have separately created a security advisory for Akka.NET Versions < 1.4.46 and < 1.5.0-alpha3 to track this issue.

Fixes and Updates

• Akka: Revert ConfigurationException due to binary incompatibility
• Akka: Upgrade to Newtonsoft.Json 13.0.1 as minimum version - resolves security issue.
• Akka: Upgrade to System.Configuration.ConfigurationManager 6.0.1 - resolves security issue.
• Akka: Upgrade to Google.Protobuf 3.21.9
• Akka.Cluster.Tools: Make sure that DeadLetters published by DistributedPubSubMediator contain full context of topic
• Akka.Streams: Remove suspicious code fragment in ActorMaterializer
• Akka.IO: Report cause for Akka/IO TCP CommandFailed events
• Akka.Cluster.Metrics: Improve CPU/Memory metrics collection at Akka.Cluster.Metrics - built-in metrics are now much more accurate.

You can see the full set of tracked issues for Akka.NET v1.5.0 here.