[devtool] inject css as styleTag rather than singletonStyleTag (#81297)
Change the style-loader injection for devtool from `singletonStyleTag` to `styleTag` (which is also default).
The original setting was configured in #81236 , @mischnic a case where the style is inserted but not applied.
Using `styleTag` will insert multi styleTag which can force it layout again when the style is added