Add core result types for fluent API pattern (Phase 1.1)

Introduces foundational types that enable the `.with_detail_response()` fluent API pattern:

- RequestMetadata: HTTP request/response metadata for diagnostics (client_request_id, correlation_id, service_request_id, http_status_code, timing_ms)
- DataverseResponse[T]: Generic response object with result and telemetry dict
- FluentResult[T]: Wrapper enabling fluent pattern - acts like result by default, returns DataverseResponse via .with_detail_response()

FluentResult implements magic methods (__iter__, __getitem__, __len__, __eq__, __bool__, __contains__, __hash__) for transparent backward compatibility.

Existing OperationResult, CreateResult, UpdateResult, DeleteResult, GetResult, PagedResult types remain unchanged for backward compatibility.

Includes comprehensive unit tests (44 tests) covering:
- RequestMetadata dataclass behavior
- DataverseResponse structure
- FluentResult wrapper with all magic methods
- Legacy type backward compatibility

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: tpellissier

src/PowerPlatform/Dataverse/core/__init__.py

@@ -8,4 +8,30 @@
 configuration, HTTP client, and error handling.
 """
 
-__all__ = []
+from .results import (
+    # New fluent API types
+    RequestMetadata,
+    DataverseResponse,
+    FluentResult,
+    # Legacy types (backward compatible)
+    OperationResult,
+    CreateResult,
+    UpdateResult,
+    DeleteResult,
+    GetResult,
+    PagedResult,
+)
+
+__all__ = [
+    # New fluent API types
+    "RequestMetadata",
+    "DataverseResponse",
+    "FluentResult",
+    # Legacy types (backward compatible)
+    "OperationResult",
+    "CreateResult",
+    "UpdateResult",
+    "DeleteResult",
+    "GetResult",
+    "PagedResult",
+]