Add markdown documentation on how to reuse existing results in a MetricsRepository

Show how to use the method reuseExistingResultsForKey and maybe show how this can be used in some example use cases:
* Experiment with checks and constraint suggestion rules
* Run different checks on some data without duplicating work, maybe a cheap one using basic analyzers first and then a second check that uses both the cheap constraints from before and some of the more expensive constraints?

Start by locating the MetricsRepository method reuseExistingResultsForKey and any existing Deequ documentation or examples that use it. Document how to reuse results, including experiments with checks and constraint suggestions and staged checks that avoid duplicate work. Done means the Markdown explains the method and includes the requested use cases.

Written by the indexing model from the issue text.