Add instrumentation for inputs keyword usage tracking

Summary

Add instrumentation to track usage of the inputs: keyword in CI/CD pipeline configurations. This enables monitoring adoption of pipeline inputs and the newer rules feature for dynamic inputs.

Events to Track

1. use_inputs_keyword_in_cicd_yaml - Triggered when a pipeline uses the inputs: keyword in the spec header
2. use_input_rules_keyword_in_cicd_yaml - Triggered when a pipeline uses rules: within an input definition

Implementation

Related MR: !214061