Scala 3 support

[jchapuis]

Now that we have removed the dependency on cats-tagless, we can finally cross-compile to Scala 3 & Scala 2.13 🎉

We had to bump the Akka version minimum requirement to 2.6.10 for the "native" Scala 3 support

Small note that the scodec helpers only supports scala 3, as maintaining both creates some complexity - so unless proven we need support for 2.13 I'm only including support for the latest version.

Resolves: #175

[codecov]

Codecov Report

Merging #285 (c93d5a3) into master (aab1582) will decrease coverage by 0.25%.
Report is 4 commits behind head on master.
The diff coverage is 97.51%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #285      +/-   ##
==========================================
- Coverage   90.15%   89.90%   -0.25%     
==========================================
  Files          71       72       +1     
  Lines         914      872      -42     
  Branches       98       98              
==========================================
- Hits          824      784      -40     
+ Misses         90       88       -2     

Files	Coverage Δ
.../scala/endless/runtime/akka/EntityPassivator.scala	87.50% <ø> (ø)
...a/endless/runtime/akka/ShardingCommandSender.scala	100.00% <100.00%> (ø)
...cala/endless/runtime/akka/deploy/AkkaCluster.scala	92.30% <ø> (ø)
...ala/endless/runtime/akka/deploy/AkkaDeployer.scala	100.00% <100.00%> (ø)
...less/runtime/akka/deploy/AkkaDurableDeployer.scala	100.00% <100.00%> (ø)
...oy/internal/DurableShardedRepositoryDeployer.scala	91.89% <100.00%> (ø)
...ternal/EventSourcedShardedRepositoryDeployer.scala	84.09% <100.00%> (ø)
...ka/deploy/internal/ShardedRepositoryDeployer.scala	100.00% <100.00%> (ø)
...less/runtime/akka/protobuf/ScalaPbSerializer.scala	80.95% <100.00%> (ø)
...ss/runtime/akka/serializer/CommandSerializer.scala	78.57% <ø> (ø)
... and 52 more

... and 5 files with indirect coverage changes