refactor: replace workbook-specific token tracking with generic telemetry logging

- Remove Azure Workbook infrastructure (bicep, KQL, JSON)
- Replace token_usage_utils with llm_token_telemetry and telemetry modules
- Update pipeline handlers and workflow executors to use new telemetry
- Update unit tests for new module structure

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Prachig-Microsoft