refactor: Split config/halfstack/global contexts from root context

[achimnol]

This PR splits RootContext into three categories of contextual objects:

• Configurations (those from etcd and local TOML files, runtime identifier like pidx)
• Halfstack connection pools (postgres and redis)
• Global stateful objects (event bus, background task manager, storage proxy connector, etc.)

Relationship:

• replaces fix: Miscalc and inefficient db access patterns of session concurrency limits #3064
• resolves Refactor RootContext to explicitly distinguish context info groups #3156 (BA-37)

Checklist: (if applicable)

• Milestone metadata specifying the target backport version
• Mention to the original issue

[achimnol]

• fix: Rewrite concurrency tracking mechanism to use Redis sets #3155
• refactor: Split config/halfstack/global contexts from root context #3154 👈 (View in Graphite)
• main

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[HyeockJinKim]

In my opinion, even if the root context is divided into substructures, the significance of refactoring diminishes if the root context is still being accessed directly.
It seems necessary to explicitly pass only the required configuration values to handlers or other modules.
Are there any tasks you are considering regarding this? @achimnol

[achimnol]

In my opinion, even if the root context is divided into substructures, the significance of refactoring diminishes if the root context is still being accessed directly. It seems necessary to explicitly pass only the required configuration values to handlers or other modules. Are there any tasks you are considering regarding this? @achimnol

Ultimately yes, but this PR is an interim step towards that goal.
I'd like to first signify whether the root context attributes are either configurations (c), global singletons (g), or database connection pools (h).

Each category would have different sharing scopes. For instance:

• config: It can be shared and accessed from anywhere.
  • Later, we may need to add an interface to reload/live-update the config values using etcd watch for the shared configs.
• halfstack: We need to first complete Refactoring from higher layers based on Protocols #3183 to categorize and make explicit dependency relationships between the global singletons whether each instance belongs to either service or repository layers. We may need to split existing classes to achieve this. Once we have a clear separation between the service and repository layers, global singletons in the repository layer could share the entire halfstack connection pools.
• global: We need to pass exactly required ones.

I think introducing an explicit hierarchy to the root context will help us to automatically replace the references across the entire manager codebase after #3183.