Fixes #12685 - Improve error handling for TSVB

[simianhacker]

This PR improves the error handling for Javascript thrown errors on the server. It also adds more details to permission errors which is caused by a missing aggregation key.

[cjcenizal]

Woah, I've never seen this state before! @snide Have you seen this?

[snide]

No but reminds me of the multiple permission display one that came in a couple days ago.

[cjcenizal]

@simianhacker How can we trigger this error to repro your screenshot?

[simianhacker]

It's the error message in TSVB. If you create a visualization with an error in it (a bad script in a calculation works really well) then you will see it.

[weltenwort]

The error message pointing the user to incorrect permissions also shows up when entering an index pattern that does not match any indices. Maybe we should include that in the message as well, e.g. "The aggregations key is missing from the response. Please check the index pattern and your permissions for reading from it."?

[thomasneirynck]

Closes #12685.

[thomasneirynck]

@simianhacker makes sense to change to add that info to the error message as well? If so, we can probably go ahead and merge this. thx,

[simianhacker]

Back ported to 6.0 with dd36884
Back ported to 6.x with 47abe12