Pull Request for Issue #35927.

Summary of Changes

This PR fixes issue #35927 and also, some invalid mark up on buttons layout of radio form field.

1. Move $attribs back to fieldset. It was moved from fieldset to dev by mistake in the PR #19946
2. Remove required attribute from fieldset because required is invalid attribute for fieldset. I think autofocus should be removed, too, because it is also invalid. But then how should we handle autofocus for radio options? For now, I leave it there
3. Fix invalid markup for label of disabled option. style="pointer-events: none"' should not be used inside class (you can see this by reviewing code)

Testing Instructions

1. Open administrator/components/com_banners/config.xml, change https://github.com/joomla/joomla-cms/blob/4.0-dev/administrator/components/com_banners/config.xml#L24-L33 to the below code to make that field disabled and use buttons layout:

<field
	name="track_impressions"
	type="radio"	
	label="COM_BANNERS_FIELD_TRACKIMPRESSION_LABEL"
	default="0"
	disabled="true"
	>
	<option value="0">JNO</option>
	<option value="1">JYES</option>
</field>

2. Login to administrator area of your site, access to Banners component, click on Options button in the toolbar to change setting of the component
3. Press Save button to save the change

Actual result BEFORE applying this Pull Request

You got fatal error because the value of that disabled field still being submitted to server (causes by invalid mark up for the field)

Expected result AFTER applying this Pull Request

Change can be saved properly. Also, please make to the appearance of the field is not changed after PR.

Documentation Changes Required

None.