Pekko runtime

[jchapuis]

Add a Pekko runtime (along the existing Akka runtime) so to allow tagless clusters be run with Pekko

[codecov]

Codecov Report

Merging #239 (bef9aaf) into master (0bf3567) will decrease coverage by 0.05%.
The diff coverage is 89.17%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #239      +/-   ##
==========================================
- Coverage   89.98%   89.93%   -0.05%     
==========================================
  Files          55       71      +16     
  Lines         589      914     +325     
  Branches       61      121      +60     
==========================================
+ Hits          530      822     +292     
- Misses         59       92      +33     

Impacted Files	Coverage Δ
.../scala/endless/runtime/akka/EntityPassivator.scala	87.50% <ø> (ø)
...a/endless/runtime/akka/ShardingCommandRouter.scala	100.00% <ø> (ø)
...cala/endless/runtime/akka/deploy/AkkaCluster.scala	92.30% <ø> (ø)
...n/scala/endless/runtime/akka/deploy/Deployer.scala	100.00% <ø> (ø)
.../endless/runtime/akka/deploy/DurableDeployer.scala	75.00% <ø> (ø)
...deploy/internal/DurableShardedEntityDeployer.scala	90.62% <ø> (ø)
...y/internal/EventSourcedShardedEntityDeployer.scala	82.05% <ø> (ø)
...ka/deploy/internal/ShardedRepositoryDeployer.scala	100.00% <ø> (ø)
...less/runtime/akka/protobuf/ScalaPbSerializer.scala	80.95% <ø> (ø)
...ss/runtime/akka/serializer/CommandSerializer.scala	78.57% <ø> (ø)
... and 24 more

... and 1 file with indirect coverage changes