akka-grpc 2.3.0 is now available under Apache license

[pjfanning]

More than 3 years since release

https://github.com/akka/akka-grpc/releases/tag/v2.3.0

We may not want all the changes. Pekko gRPC has always supported Scala 3, for instance. Better if any changes for Pekko gRPC can be justified by need as opposed to blindly copying everything.

[pjfanning]

@raboof do you think it is useful to copy over akka/akka-grpc#1665 and the related akka/akka-grpc#1740 changes?

[Philippus]

https://github.com/akka/akka-grpc/releases/tag/v2.3.1 is now also Apache 2.0.

I've ported one of the PR's: #682