Support SBR-decided shutdowns

[jchapuis]

The SBR can decide that the node needs to exit, in which case Akka initiates the application shutdown. We need to make sure that all cats-effect resources are released in such cases. This PR improves mechanisms around application shutdown.

[codecov]

Codecov Report

Merging #222 (8224bbe) into master (66bd15e) will decrease coverage by 0.78%.
The diff coverage is 68.96%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #222      +/-   ##
==========================================
- Coverage   91.15%   90.37%   -0.78%     
==========================================
  Files          55       55              
  Lines         565      582      +17     
  Branches        3        4       +1     
==========================================
+ Hits          515      526      +11     
- Misses         50       56       +6     

Impacted Files	Coverage Δ
example/src/main/scala/endless/example/Main.scala	0.00% <0.00%> (ø)
...n/scala/endless/runtime/akka/deploy/Deployer.scala	100.00% <ø> (ø)
.../endless/runtime/akka/deploy/DurableDeployer.scala	75.00% <ø> (ø)
...le/src/main/scala/endless/example/ExampleApp.scala	96.20% <75.00%> (-1.17%)	⬇️
...cala/endless/runtime/akka/deploy/AkkaCluster.scala	92.30% <92.30%> (-7.70%)	⬇️
...ka/deploy/internal/ShardedRepositoryDeployer.scala	100.00% <100.00%> (ø)