Minor follow-up work after adding extended attributes as the default everywhere

We don't convert / clean logging body's the way we do attribute values, but I think it makes sense to do something very similar because a logging body is an AnyValue, same as attribute value.

We can cleanup docs/conf.py a bit by removing the AnyValue import / built in override, and instead import AnyValue at runtime in the modules that annotate with it.

One thing that's missing from the spec is if leaf nodes should count towards the max attribute total count, I think that is the intent but it was not clearly documented (see https://github.com/open-telemetry/opentelemetry-python/pull/4587 and https://github.com/open-telemetry/opentelemetry-python/pull/4587) -- I can clarify and clean that up in a follow up PR though, as this one is already pretty big..

Delete stale and unnecessary .pyi file: opentelemetry-sdk/src/opentelemetry/sdk/util/init.pyi -- may need to add type annotations to the corresponding file if they are missing

Start with the referenced logging implementation in opentelemetry-sdk/src/opentelemetry/sdk/_logs/_internal/init.py and compare its attribute-value handling with logging bodies. Review docs/conf.py and opentelemetry-sdk/src/opentelemetry/sdk/util/init.pyi for the requested cleanup. Done means body handling follows the intended AnyValue cleanup, the stale type stub is removed or its annotations are preserved, and the documentation configuration no longer needs the listed override.