Add markdown documentation for an AnalysisRunner example

The AnalysisRunner is our main entry point for calculating metrics in a scenario where you don't want to write unit tests but want to do something different with the metrics. We need to make the distinction between the AnalysisRunner and the ColumnProfilerRunner clear.

The entry points named are AnalysisRunner and ColumnProfilerRunner; start by locating their existing documentation and examples in the repository. Add a Markdown example explaining when to use AnalysisRunner instead of ColumnProfilerRunner and verify that the distinction and non-unit-test metrics workflow are clear.

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