Supports `styleOptions` override on a per-activity basis

[compulim]

Is your feature request related to a problem?

Will be great if every activity can have their own set of styleOptions. For example, avatar image and bubble color could be different on every activity.

Describe the suggestion or request in detail

Related to #5184.

Could use activity.channelData.webChat.styleOptions.*.

Describe alternatives you have considered

No response

Additional context

No response