JetBrains: Decrease display limit 1500→200

Created by: vdavid

Fixes https://github.com/sourcegraph/sourcegraph/issues/37818

Context:

• Our streaming search back-end API provides display-limit to customize the total number of search results returned.
• Our streaming search front-end API did not provide such a setting, however. It was a fixed 1500.

Change: I've created an optional setting in our front-end API to customize this (with a default of 1500), and set the JetBrains plugin to use 200 for it.

Why 200? → "Find in Files" limits its matches to 100, so I think 200 will be sufficient for our users. Caveat: "Find in Files" allows opening all search results in a panel, which we don't at the moment, so after the change, the rest of the results won't be accessible. I think we can live with this, though. We can increase it on-demand if we're getting feedback on this. Right now, this should help with performance issues that one of our testers experienced.

Test plan

Same stuff, just fewer results: