Optimize adding contributors to evaluation

[fekoch]

When adding a contributor to an evaluation on staff/evaluation/:id/edit via the "add another"-button, the page sometimes hangs for 2 to 4 seconds.

Initial profiling suggest, that the culprit may be the auto-fill system of the browser. (Specifically, getFormInfo() / getFormAutofillConfidences().)

As those forms should not use a browser provided form of auto completion, we should look into preventing these calls.

[richardebeling]

If it is the browser autocompletion system: We already have various places in code where we disable that.

I would be very interested why we make the autocompletion struggle so much. From my understanding, the "add another" button should just add a handful of new inputs, I would expect autocompletion to be done with them in a millisecond.

[fekoch]

If it is the browser autocompletion system: We already have various places in code where we disable that.

I am not sure what else it could be. Running the profiler in a clean Firefox instance mostly samples ChromeUtils.getFormAutofillConfidences() for the hang duration.