revert models.py changes, use raw dicts without modifying codegen

Python dataclasses don't enforce types at runtime, so factory
functions can accept raw dicts directly. This removes the need to
change TextMapPropagator from a @DataClass to a TypeAlias.

Assisted-by: Claude Opus 4.6 (1M context)

Author: MikeGoldsmith

opentelemetry-sdk/src/opentelemetry/sdk/_configuration/models.py

@@ -573,10 +573,12 @@ class SpanProcessor:
     simple: SimpleSpanProcessor | None = None
 
 
-# Diverges from codegen: TextMapPropagator is typed as dict[str, Any] rather
-# than a dataclass so that unknown propagator names (plugin/custom propagators)
-# are preserved as dict keys through the config pipeline.
-TextMapPropagator: TypeAlias = dict[str, Any]
+@dataclass
+class TextMapPropagator:
+    tracecontext: TraceContextPropagator | None = None
+    baggage: BaggagePropagator | None = None
+    b3: B3Propagator | None = None
+    b3multi: B3MultiPropagator | None = None
 
 
 @dataclass