Type operators in promoteOccName (#24570)

Type operators differ from term operators in that they are lexically
classified as (type) constructors, not as (type) variables.

Prior to this change, promoteOccName did not account for this
difference, causing a scoping issue that affected RequiredTypeArguments.

  type (!@#) = Bool
  f = idee (!@#)      -- Not in scope: ‘!@#’  (BUG)

Now we have a special case in promoteOccName to account for this.