.NET: Reconsider the merging precedence of properties on ChatClientAgentRunOptions and ChatClientAgentRunOptions.ChatOptions where they overlap

[westey-m]

We have some settings that are both on ChatClientAgentRunOptions directly and on ChatClientAgentRunOptions.ChatOptions, e.g. AllowBackgroundResponses.
Where the value is set on both the AgentRunOptions and ChatOptions, and the values differ, we have to pick which is ultimately used.

See this comment for more info.