Improve `<SvgIcon>` to make it output `svg` node and optimize performance (#23570)

Before, the Vue `<SvgIcon>` always outputs DOM nodes like: 

```html
<span class="outer-class">
    <svg class="class-name-defined" ...></svg>
</span>
```

The `span` is redundant and I guess such layout and the inconsistent
`class/class-name` attributes would cause bugs sooner or later.

This PR makes the `<SvgIcon>` clear, and it's faster than before,
because it doesn't need to parse the whole SVG string.

Before: 

<details>

![image](https://user-images.githubusercontent.com/2114189/226156474-ce2c57cd-b869-486a-b75b-1eebdac8cdf7.png)

</details>

After:

![image](https://user-images.githubusercontent.com/2114189/226155774-108f49ed-7512-40c3-94a2-a6e8da18063d.png)

---------

Co-authored-by: silverwind <me@silverwind.io>

1 files changed, 21 insertions, 1 deletions

diff --git a/web_src/js/svg.test.js b/web_src/js/svg.test.js
index c5d6d07535..5db2f65ac8 100644
--- a/web_src/js/svg.test.js
+++ b/web_src/js/svg.test.js
@@ -1,8 +1,28 @@
 import {expect, test} from 'vitest';
-import {svg} from './svg.js';
+import {svg, SvgIcon, svgParseOuterInner} from './svg.js';
+import {createApp, h} from 'vue';
 
 test('svg', () => {
   expect(svg('octicon-repo')).toMatch(/^<svg/);
   expect(svg('octicon-repo', 16)).toContain('width="16"');
   expect(svg('octicon-repo', 32)).toContain('width="32"');
 });
+
+test('svgParseOuterInner', () => {
+  const {svgOuter, svgInnerHtml} = svgParseOuterInner('octicon-repo');
+  expect(svgOuter.nodeName).toMatch('svg');
+  expect(svgOuter.classList.contains('octicon-repo')).toBeTruthy();
+  expect(svgInnerHtml).toContain('<path');
+});
+
+test('SvgIcon', () => {
+  const root = document.createElement('div');
+  createApp({render: () => h(SvgIcon, {name: 'octicon-link', size: 24, class: 'base', className: 'extra'})}).mount(root);
+  const node = root.firstChild;
+  expect(node.nodeName).toEqual('svg');
+  expect(node.getAttribute('width')).toEqual('24');
+  expect(node.getAttribute('height')).toEqual('24');
+  expect(node.classList.contains('octicon-link')).toBeTruthy();
+  expect(node.classList.contains('base')).toBeTruthy();
+  expect(node.classList.contains('extra')).toBeTruthy();
+});