Add support for nested-fieldset control.

web/pgadmin/static/js/components/FieldSet.jsx

@@ -0,0 +1,35 @@
+import { makeStyles } from '@material-ui/core';
+import React from 'react';
+import clsx from 'clsx';
+import PropTypes from 'prop-types';
+import CustomPropTypes from '../custom_prop_types';
+
+const useStyles = makeStyles((theme)=>({
+  fieldset: {
+    padding: theme.spacing(0.5),
+    borderRadius: theme.shape.borderRadius,
+    backgroundColor: 'inherit',
+    border: '1px solid ' + theme.otherVars.borderColor,
+  },
+  legend: {
+    width: 'unset',
+    fontSize: 'inherit',
+    fontWeight: 'bold',
+  }
+}));
+
+export default function FieldSet({title='', className, children}) {
+  const classes = useStyles();
+  return (
+    <fieldset className={clsx(classes.fieldset, className)}>
+      <legend className={classes.legend}>{title}</legend>
+      {children}
+    </fieldset>
+  );
+}
+
+FieldSet.propTypes = {
+  title: PropTypes.string,
+  className: CustomPropTypes.className,
+  children: CustomPropTypes.children,
+};