Adapt Livebook's runtime configuration for Meadow

[mbklein]

Summary

The Hush module made our configuration super complicated, and resulted in near constant compilation and runtime warnings about redefining modules. Livebook uses a pretty good pattern for runtime configuration that I've tried to replicate here. It was tricky managing different environments that all have some level of dynamic/runtime config, or whose configuration might be overwritten by the top-level runtime config, but I think I came up with a reasonable middle ground. It's still a departure from standard Elixir practice, but it's better than it was.

Specific Changes in this PR

• Remove hush and hush_aws_secretsmanager dependencies
• Create Meadow.Runtime module with convenience functions for retrieving AWS and environment secrets
• Create modules for the same kind of hierarchical runtime config that config/*.exs does for compile-time config:
  • Meadow.Runtime.Config
  • Meadow.Runtime.{Dev, Test, Prod}
  • Meadow.Runtime.Release
  • Meadow.Runtime.Pipeline
• Minimal updates to lib and test code to account for the new runtime config (mostly the disappearance of Hush)
• Update to ueberauth_nusso v2.0.0 to support a split between compile-time Ueberauth config and runtime Ueberauth strategy config

Version bump required by the PR

See Semantic Versioning 2.0.0 for help discerning which is required.

• Patch
• Minor
• Major

Steps to Test

Just run it and make sure everything's behaving, and look over the new config modules to make sure we all understand where any new/changed config would go.

🚀 Deployment Notes

Note - if you check any of these boxes go to the (always open) main <- staging PR and add detailed notes and instructions to help out others who may end up deploying your changes to production

• Backward compatible API changes
  • Database Schema changes
  • GraphQL API
  • Elasticsearch API
  • Ingest Sheet
  • CSV metadata export/update API
  • Shared Links export API
• Backwards-incompatible API changes
  • Database Schema changes
  • GraphQL API
  • Elasticsearch API
  • Ingest Sheet
  • CSV metadata export/update API
  • Shared Links export API
• Requires data migration
• Requires database triggers disabled during deployment/migration
• Requires reindex
• Terraform changes
  • Adds/requires new or changed Terraform variables
• Pipeline configuration changes (requires mix meadow.pipeline.setup run)
• Requires new variable added to miscellany
• Specific deployment synchronization instructions with other apps/API's
• Other specific instructions/tasks

Tested/Verified

• End users/stakeholders