refactor: remove dependency of classnames and className and customStyle props

[b2nil]

This PR is mainly intended to:

1. Use computed classes to replace the dependency of classnames

   const rootClasses = computed(() => ({
   'at-xxx': true,
   }))

2. Use class and style to replace the props of className and customStyle

   <at-card class="custom-class" style="height: 20px;">...</at-card>

   The props of class and style will be merged to the attrs of the component's root node:

   setup(props, { slots, attrs }) {
   h(View, mergeProps(attrs, {
    class: rootClasses.value
   }), slots.default())
   }

3. and some other minor fixes