[UI/UX] Code folding for tag that span on multiple lines

[ficristo]

In #12521 @thehogfather change the behavior of code folding to match the CodeMirror one.
So now when a tag span on multiple lines you have two code folding triangles.

@redmunds proposed an alternative.
Another option would be to collapse both tag attributes and tag contents something like this:

For reference 1.7 behaviour:

Opening this to review this aspect.

[ficristo]

/cc @larz0