Label styling regression introduced by 9d63cfc while fixing date description spacing

Problem/Motivation

A regression appears to have been introduced by commit 9d63cfc993ed8a6e2c062ba9231d8dd6b2e6d90f
(#3573981: An empty line is added between a date form element and its description).

That commit fixes the date/help-text spacing problem, but it also changes the label selector in

css/components/
  form.css

from:

label {
  display: table;
  margin: 0 0 0.1em;
  padding: 0;
  font-weight: bold;
  }

to:

.label {
  display: table;
  margin: 0 0 0.1em;
  padding: 0;
  font-weight: bold;
  }

Standard Drupal form labels are still rendered as normal <label> elements, for example:

<div class="js-form-item form-item js-form-type-textfield form-type-textfield js-form-item-title form-item-
  title">
  <label for="edit-title">Titel</label>
  <input data-drupal-selector="edit-title" type="text" id="edit-title" name="title" value="" size="30" maxlength="128"
  class="form-text">
  </div>

The label does not have class="label", so the styling is no longer applied.

As a result:

- readability is reduced
- this can also affect accessibility

This is visible in standard admin/editorial forms and is not limited to a special edge case.

Steps to reproduce

1. Open a standard Drupal admin form with a normal textfield, for example a node edit form.
2. Inspect the rendered label element.
3. Compare Seven before and after commit 9d63cfc993ed8a6e2c062ba9231d8dd6b2e6d90f.
4. Observe that the markup is still a normal <label>, but the styling no longer applies because the CSS
now targets .label instead of label.

Proposed resolution

Restore the styling for standard rendered form labels, or otherwise ensure that the equivalent styling still applies
to normal Drupal <label> elements.

Additional information

This looks like an unintended side effect of the fix for #3573981 rather than a separate intended UI
change.
This change to breaks the layout of the publication date module and sheduler module where descriptions now overlap fields.

Screenshots