[All platforms] Ability to associate a person identity with any element

What platform is your feature request related to? (Delete other platforms).

All platforms. JS is PO.

Is your feature request related to a problem? Please describe.
Search needs to integrate the M365 persona card with custom search results, which are rendered using Adaptive Cards. The need is not to have a specific person element but instead to be able to associate a person's identity with any element in the card, including individual text runs in a RichTextBlock.

When a person's identity is associated with an element, that element would trigger an onElementHover(sender: CardElement) event that the consuming application can handle to implement whichever behavior they need, including popping up the live persona card.

Describe the solution you'd like
Allow card authors to associate a "person" entity with any element. Examples:

{
    "type": "AdaptiveCard",
    "$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
    "version": "1.3",
    "body": [
        {
            "type": "TextBlock",
            "text": "John Doe",
            "entity": {
                "type": "Person",
                "id": "john.doe@contoso.com",
                "displayName": "John Doe"
            }
        },
        {
            "type": "Image",
            "url": "https://...",
            "entity": {
                "type": "Person",
                "id": "john.doe@contoso.com",
                "displayName": "John Doe"
            }
        },
        {
            "type": "RichTextBlock",
            "inlines": [
                {
                    "type": "TextRun",
                    "text": "Owner: "
                },
                {
                    "type": "TextRun",
                    "text": "John Doe",
                    "entity": {
                        "type": "Person",
                        "id": "john.doe@contoso.com",
                        "displayName": "John Doe"
                    }
                }
            ]
        }
    ]
}

On the SDK side, expose an API to handle the hover event:

card.onElementHover(sender: CardElement) {
  let personEntity = sender.entities.find("Person");

  if (personEntity) {
    popupPersonaCard(sender.renderedElement, personEntity.id);
  }
}

Start by reviewing the SDK entry points for CardElement, TextBlock, Image, RichTextBlock, and TextRun, then compare how events are exposed across the all-platforms implementations. Use the issue's JSON examples and TypeScript onElementHover sketch to define the supported entity locations and verify the behavior in each affected platform.