…n support

## Summary
  - Adds W3C trace context propagation to the Databricks C# driver via HTTP
  headers
  - Makes trace propagation configurable with options for enablement, header
   names, and trace state
  - Integrates with existing ADBC tracing infrastructure to support
  distributed tracing

  ## Details
  This PR implements W3C Trace Context (traceparent/tracestate) propagation
  for the Databricks C# driver. When distributed tracing is enabled, the
  driver now propagates trace context to Databricks servers, enabling
  end-to-end request tracing across the distributed system.

  ### Implementation
  - Added `TracingDelegatingHandler` to inject trace headers into HTTP
  requests
  - Integrated handler into the existing HTTP pipeline in
  `DatabricksConnection`
  - Added configuration options:
    - `adbc.databricks.trace_propagation.enabled` (default: true)
    - `adbc.databricks.trace_propagation.header_name` (default:
  "traceparent")
    - `adbc.databricks.trace_propagation.state_enabled` (default: false)

  ### Behavior
  1. If `Activity.Current` exists, uses its trace context
  2. Falls back to trace parent from connection options
  (`adbc.telemetry.trace_parent`)
  3. Optionally includes trace state header when enabled
  4. Supports custom header names for compatibility with different systems

  ## Test plan
  - [x] Added comprehensive unit tests for `TracingDelegatingHandler`
  - [x] Added tests for configuration parsing in `DatabricksConnectionTest`
  - [x] Verified trace header propagation with mock HTTP handlers
  - [x] Tested with and without active activities
  - [x] Tested custom header names and trace state propagation
  - [ ] Manual testing with actual Databricks instance