(core) Update UI for formula and column label/id in the right-side panel.

Summary:
- Update styling of label, id, and "derived ID from label" checkbox.
- Implement a label which shows 'Data Column' vs 'Formula Column' vs 'Empty Column',
  and a dropdown with column actions (such as Clear/Convert)
- Implement new formula display in the side-panel, and open the standard
  FormulaEditor when clicked.
- Remove old FieldConfigTab, of which now very little would be used.
- Fix up remaining code that relied on it (RefSelect)

Test Plan: Fixed old tests, added new browser cases, and a case for a new helper function.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2757

app/client/components/BaseView.js

@@ -290,6 +290,18 @@ BaseView.prototype.activateEditorAtCursor = function(input) {
   }
 };
 
+/**
+ * Move the floating RowModel for editing to the current cursor position, and return it.
+ *
+ * This is used for opening the formula editor in the side panel; the current row is used to get
+ * possible exception info from the formula.
+ */
+BaseView.prototype.moveEditRowToCursor = function() {
+  var rowId = this.viewData.getRowId(this.cursor.rowIndex());
+  this.editRowModel.assign(rowId);
+  return this.editRowModel;
+};
+
 // Copy an anchor link for the current row to the clipboard.
 BaseView.prototype.copyLink = async function() {
   const rowId = this.viewData.getRowId(this.cursor.rowIndex());