refactor: split multi_provider.py into a package with _strategies and _provider modules

Signed-off-by: Jonathan Norris <jonathan.norris@dynatrace.com>

Author: jonathannorris

openfeature/provider/multi_provider/__init__.py

@@ -0,0 +1,16 @@
+from ._provider import MultiProvider, ProviderEntry
+from ._strategies import (
+    ComparisonStrategy,
+    EvaluationStrategy,
+    FirstMatchStrategy,
+    FirstSuccessfulStrategy,
+)
+
+__all__ = [
+    "ComparisonStrategy",
+    "EvaluationStrategy",
+    "FirstMatchStrategy",
+    "FirstSuccessfulStrategy",
+    "MultiProvider",
+    "ProviderEntry",
+]