feat(BA-24): Split redis config for each connection pool

[seedspirit]

resolves #3195 (BA-24)

Checklist: (if applicable)

• Milestone metadata specifying the target backport version
• Mention to the original issue
• Installer updates including:
  • Fixtures for db schema changes
  • New mandatory config options
• Update of end-to-end CLI integration tests in ai.backend.test
• API server-client counterparts (e.g., manager API -> client SDK)
• Test case(s) to:
  • Demonstrate the difference of before/after
  • Demonstrate the flow of abstract/conceptual models with a concrete implementation
• Documentation
  • Contents in the docs directory
  • docstrings in public interfaces and type annotations

[HyeockJinKim]

Why is this setting necessary?

[seedspirit]

As redis config allows extra fields, we need to add what is standard and what is not standard fields.
The only way I know of to add a field that is not predefined in the dataclass is to have it as a set or dict, as it is currently. Is there any other way?

redis_config_iv = t.Dict({
    t.Key("addr", default=redis_default_config["addr"]): t.Null | tx.HostPortPair,
    ...
    t.Key("override_configs", default=None): t.Null
    | t.Mapping(
        t.String,
        t.Dict({
            t.Key("addr", default=redis_default_config["addr"]): t.Null | tx.HostPortPair,
            ...
        }).allow_extra("*"),
    ),
}).allow_extra("*")

[HyeockJinKim]

Avoid using abbreviations like RLIM.