Add Semantic Kernel to user agent and Semantic Kernel Version header to OpenAPI plugin requests

[madsbolaris]

To allow downstream applications know that Semantic Kernel made an HTTP request from an OpenAPI plugin, we should provide the same headers and user agent as we do for Azure OpenAI

[moonbox3]

We do this today in Python: https://github.com/microsoft/semantic-kernel/blob/0fda22e8f547e100e4dd9b8b1307142af42a251a/python/semantic_kernel/connectors/openapi_plugin/openapi_runner.py#L154C9-L157C1

[madsbolaris]

@SergeyMenshykh, do we already do this in .NET?

[markwallace-microsoft]

Yes, we do this, here's the relevant code: https://github.com/microsoft/semantic-kernel/blob/main/dotnet/src/Functions/Functions.OpenApi/RestApiOperationRunner.cs#L187-L189

Note: This can be overridden.