Visualize individual timeRange not working properly

[timroes]

The way individual time ranges are handled for visualizations is somewhere between kind of broken and broken.

You can currently specify a timeRange when embedding a visualization using the loader (i.e. the way you should embed a visualization), so that the visualization should use that time range instead of the global one defined by the time picker.

We currently read this out in visualize.js and attach it to the search source, that is passed to the request handler. Since the searchSource is only used by the courier request handler and not others (TSVB, timelion, Vega), those will need different access to the configured time range.

Earlier we set it to vis.params.timeRange and those request handler checked this one before accessing the global time range. Since #15998 we rather attach a method to vis, that should (but currently isn't) be used from within the different request handlers. That's also why currently all those non default request handlers are broken for individual time ranges.

I think it would make more sense to explicitly pass the time range to the request handler, instead of attaching this to the vis object.

This issue is related to #16641 in a way that we should also consider always requiring to specify the time range via the loader and not pass it via searchSource inheritance, that would anyway be ignored by non default request handlers.

[timroes]

We should also define, in what format requests handlers should expect the actual timeRange value to be. Currently it seems like every request handler expects it in a slightly different format, which means that would anyway never ever have worked properly.