fix: accept lifecycle hyperparameter generators

[egillax]

Summary

• allow createHyperparameterSettings() to accept lifecycle generator objects with initialize() and getNext()
• keep function generators supported and document both generator contracts explicitly
• add regression coverage for generator objects passed through the constructor

Fixes #665

Testing

• Rscript -e 'devtools::test(filter = "hyperparameterSettings")'

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.74%. Comparing base (aee14bf) to head (fdeb5a4).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #668   +/-   ##
========================================
  Coverage    89.73%   89.74%           
========================================
  Files           49       49           
  Lines        13691    13704   +13     
========================================
+ Hits         12286    12299   +13     
  Misses        1405     1405           

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