An error field in FunctionExecutionResult to explicitly indicate errors occurred during execution

[ekzhu]

[wistuba]

I think, I'll be able to start with this one. Does this require special alignment? I would simply add a boolean field to FunctionExecutionResult and set it accordingly. I can let it default to "no error" given that this isn't a field used by every LLM. Any alternative suggestions?

[ekzhu]

Starting with just a Boolean field is good. Let's add a field "has_error" to indicate whether the result was error.

Please also add a unit test for checking errors during tool execution in the autogen-core package.