[WIP] [RFC] feat(NcIcon): add a generic component and utils for icons

[ShGKme]

☑️ Resolves

• Fix #…

Add a generic component to display icons in all supported formats.

Designed to develop components with a single icon prop and slot, supporting all the icon types:

• A Vue component icon like vue-material-design-icons/Account.vue
• An SVG icon like @mdi/svg/svg/account.svg
• A path icon like @mdi/js/account.js
• An URL icon like https://path/to/icon.svg or data:image/svg+xml;base64,...
• A class icon like icon-account

With NcIcon

<script setup lang="ts">
// Define a single `icon` 
defineProps<{
  icon?: IconGeneric,
}>()
</script>

<template>
  <button class="button">
    <span class="button__icon">
      <!-- Passing icons via slot is still possible -->
      <slot name="icon">
        <!-- A single node for all the cases -->
        <NcIcon v-if="icon" :icon>
      </slot>
    </span>
  </button>
</template>

Without

<script setup lang="ts">
// Many props for different icons
defineProps<{
  icon: string,
  iconPath: string,
}>()
</script>

<template>
  <button class="button">
    <span class="button__icon">
      <slot name="icon">
        <!-- Requires implementation for each case -->
        <span v-if="icon" :class="icon" />
        <NcIconSvgWrapper v-else-if="iconPath" :path="iconPath" />
      </slot>
    </span>
  </button>
</template>

Why add component icon type and not use <template #icon>?

Having icon as a prop even for a component allows passing it in 1 line instead of passing slot in 3-4 lines. Might be useful in some cases.

<script setup>
import IconAdd from 'vue-material-design-icons/Add.vue'
</script>

<template>
  <!-- before -->
  <NcButton :aria-label="t('Add')">
    <template #icon>
      <IconAdd />
    </template>
  </NcButton>

  <!-- after -->
  <NcButton :aria-label="t('Add')" :icon="IconAdd" />
</template>

🖼️ Screenshots

🏚️ Before	🏡 After
B	A

🚧 Tasks

• ...

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 3️⃣ Backport to next requested with a Vue 3 upgrade