feat: add pipeline_resolver_execution_paths

[k1LoW]

This pull request adds a new pipeline metric, pipeline_resolver_execution_paths_total, which calculates the total number of possible execution paths for pipeline resolvers based on the number of steps and associated tests. The metric is integrated into the codebase, thoroughly documented, and covered by comprehensive tests, including edge cases and complex scenarios.

Pipeline Metrics Enhancements:

• Added a new metric, pipeline_resolver_execution_paths_total, to count the total number of execution paths for all pipeline resolvers. This is calculated as steps^tests for each resolver, reflecting the number of testable step combinations. [1] [2]
• Updated the PipelineStepOperation struct and resource loading to include the Test field, enabling accurate calculation of execution paths. [1] [2]

Documentation Updates:

• Expanded the README.md to document the new metric, explain its calculation, and clarify its significance.

Testing Improvements:

• Added and updated tests in tailor/metrics_test.go to verify the correct calculation of pipeline_resolver_execution_paths_total across a variety of scenarios, including edge cases and large numbers. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Internal Refactoring:

• Imported the math package in tailor/metrics.go to support power calculations for the new metric.

These changes provide deeper insights into pipeline complexity and test coverage, improving the usefulness of the metrics output for users.

[github-actions]

Code Metrics Report

Coverage	Code to Test Ratio
34.7%	1:1.8

Code coverage of files in pull request scope (22.0%)

Files	Coverage
tailor/metrics.go	100.0%
tailor/resource.go	0.0%

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Reported by octocov