forms: show error under title if any fields are unchecked when the user attempts to continue

refs #14565
form: move the error message to a proper location

refs #14565
form error: make the new error stand out in red

refs #14565
form error: an even better location

refs #14565
form error: an even better location for the form error message

refs #14565
form error: add a newline

refs #14565
Merge branch 'bug/14565'