JavaScript performance is slow on View editor

[zackkatz]

1. Add hundreds of fields to a View
2. Save the View
3. See as the page paints and then it takes a long time for the View Configuration tabs to load

When profiling the page, most of the load time comes from a single method:toggleRequired.

In addition, Gravity Forms is initializing Merge Tags automatically for each field, which adds a lot of overhead. This is due to .merge-tag-support being added to fields. We fixed much of this in 85b6926a9437d3bac4ac72e0c0743adf281951c0, but didn't finish the job. See video of this in action.

• [x] Optimize toggleRequired
• [x] Only initialize Merge Tags when-needed

[zackkatz]

I'm sharing with affected customers. Waiting to hear back before closing.