[6.x] Replicator Display Fixes

[JayGeorge]

Description of the Problem

As per #13616, when you hide the replicator field label, the top line should probably also be hidden:

What this PR Does

• Hides the first connector line when the label is hidden, which closes Top replicator line should be hidden when display label is hidden #13616

Some additional things:

• Adds a tooltip for the show/hide display label button
• Hiding labels shouldn't remove the text from the publish form, instead they're now hidden with a screenreader-only class of sr-only

How to Reproduce

1. Add a replicator fieldtype
2. Toggle the display name in the field options
3. The connector line is still visible

[jasonvarga]

Looks like this hides more than just the first one.

[JayGeorge]

This should be fixed now. I added a couple more things while I was here and updated the PR description.