[4.0] Update buttons.php layout to latest Bootstrap 5 markup, also added LEGEND markup (#32367)

* Update buttons.php

Updated layout file according to Bootstrap 5 new markup
* the `active` class no longer required for the label
* the `<input>` is no longer inside the `<label>` element
* the new markup requires no `bootstrap.Button` plugin functionality anymore

Details on the updated markup
https://getbootstrap.com/docs/5.0/components/button-group/#checkbox-and-radio-button-groups

* Update buttons.php

Regarding #32367 (comment)

* Update buttons.php

LoL typo

* Update buttons.php

Changes: 
* Reverting to previous as explained [here](#32367 (comment)), now `class="btn-group btn-group-yesno"` is necessary to create a switcher with `type="Radio"` field with the `buttons` layout
* added `<legend>` as mentioned [here](#32367 (comment))
* both `.switcher__legend` and the new `radio__legend` additional styling is irrelevant since both elements use `.visually-hidden`, the `.switcher__legend` is now redundant

* Update buttons.php

Author: thednp

layouts/joomla/form/field/radio/buttons.php

@@ -79,6 +79,9 @@
 }
 ?>
 <fieldset id="<?php echo $id; ?>" >
+	<legend class="visually-hidden">
+		<?php echo $label; ?>
+	</legend>
 	<div <?php echo implode(' ', $attribs); ?>>
 		<?php foreach ($options as $i => $option) : ?>
 			<?php
@@ -104,7 +107,6 @@
 				$optionClass = trim($optionClass . ' ' . $disabled);
 			}
 			$checked     = ((string) $option->value === $value) ? 'checked="checked"' : '';
-			$optionClass .= $checked ? ' active' : '';
 
 			// Initialize some JavaScript option attributes.
 			$onclick    = !empty($option->onclick) ? 'onclick="' . $option->onclick . '"' : '';
@@ -116,8 +118,8 @@
 			<?php if ($required) : ?>
 				<?php $attributes[] = 'required'; ?>
 			<?php endif; ?>
+			<input<?php echo $classToggle; ?> type="radio" id="<?php echo $oid; ?>" name="<?php echo $name; ?>" value="<?php echo $ovalue; ?>" <?php echo implode(' ', $attributes); ?>>
 			<label for="<?php echo $oid; ?>" class="<?php echo trim($optionClass . ' ' . $style); ?>">
-				<input<?php echo $classToggle; ?> type="radio" id="<?php echo $oid; ?>" name="<?php echo $name; ?>" value="<?php echo $ovalue; ?>" <?php echo implode(' ', $attributes); ?>>
 				<?php echo $option->text; ?>
 			</label>
 		<?php endforeach; ?>