feat(VaTreeView): add selected node class

[mengqiuleo]

closes #3456

add active property in treeNodeClassComputed, and control active with selectedNodeComputed.value === props.node.id, add style for active class.

Description

active class style is consistent with hover style

Markup:

```vue const treeNodeClassComputed = useBem('va-tree-node', () => ({ disabled: !!props.node.disabled, active: selectedNodeComputed.value === props.node.id, })) ``` ```scss &--active > &-root::before { border-radius: var(--va-tree-node-border-radius); opacity: var(--va-tree-node-interactive-bg-opacity); } ```

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Improvement/refactoring (non-breaking change that doesn't add any feature but make things better)

[m0ksem]

I'll merge this PR to include in next release, we can extend it later if needed.

[codeonmoon]

@m0ksem - Could you please let us know how to use this merged feature?

[raizdev]

I see this is implemented? @m0ksem how can I use this feature? I don't see active class in the DOM for selectedNodes