Add hideAvatar to onFetchAvatarPersonaData API

[Leah-Xia-Microsoft]

What

• This PR is to add the ability to hide the entire avatar element in the composite level.
• Also at the component level, if Contoso developer passes in an empty element <></> to the onRenderAvatar, this PR removes the unnecessary left margin
• Since we're only adding a new optional prop to the onFetchAvatarPersonaData API, it won't be a breaking change

Why

How Tested

Process & policy checklist

• I have updated the project documentation to reflect my changes if necessary.
• I have read the CONTRIBUTING documentation.

Is this a breaking change?

• This change causes current functionality to break.

[github-actions]

CallWithChat bundle size is not changed.

• Current size: 12401112
• Base size: 12401112
• Diff size: 0

[github-actions]

Chat bundle size is increased❗.

• Current size: 1777363
• Base size: 1777255
• Diff size: 108

[github-actions]

Calling bundle size is not changed.

• Current size: 12401100
• Base size: 12401100
• Diff size: 0

[github-actions]

Failed to pass the composite UI Test. If this PR is for UI change and the error is snapshot mismatch, please add "update_snapshots" label to the PR for updating the snapshot.

[github-actions]

Failed to pass the UI Test. If this PR is for UI change and the error is snapshot mismatch, please add "update_snapshots" label to the PR for updating the snapshot.

[github-actions]

Storybook 8 URL https://60c7ae6891f0e90039d7cd54-gnyiehyneh.chromatic.com/