use Apache Pekko instead of Akka

[pjfanning]

Most of the Apache Pekko jars are now released. A decent number of 3rd party libs now also support Pekko.

https://www.lightbend.com/akka/license-faq

[bdoyle0182]

I'll likely be the one that ends up tackling this once I have bandwidth. The hard part is new clusters will have to be formed so it's technically going to be a breaking changed. We've been planning a 2.0 release for a while with our new scheduling algorithm, we should probably revisit that.

[style95]

I am also interested in this issue.

@bdoyle0182 Do you mean we have to release the openwhisk 2.0 before migrating to Pekko?