Add a configuration option for "End experiment"

[benaslater]

Is your feature request related to a problem? Please describe.
In human participant experiments it would be useful to have a way to tell AAI when the experiment should end. Currently people do this by adding a 'sink' config with no time limit, but we could have a end-after-config-file or even an end-after-n-loops-of-the-config-file config options

Additional context
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