Record test duration and display in the elementary docs

[alsaenko]

Elementary records model run duration and displays the results in the elementary docs. See the following example:

Is it also possible to record run duration (i.e. execution_time) for dbt tests and display the durations in the docs?

Use case: We would like to be able to easily profile/inspect test execution times to identify bottlenecks and areas of improvement. For example, if a particular test takes a long time to run, we might want to improve the model and potentially apply partitioning, clustering.