Add `AdditionalInfo` property to report

[tevoinea]

For teams that create their own crash reports, they would like to have additional properties to use in their notification templates.

We can add an Dictionary<string, string> AdditionalInfo to the Report object. https://github.com/microsoft/onefuzz/blob/d99960323de7336e0463f92babb80ebc841fa627/src/ApiService/ApiService/OneFuzzTypes/Model.cs#L489-L513

Then in a notification template, someone could reference is by doing something like report.additional_info.my_custom_field

AB#164905

[DrChat]

To further inform the implementation, we are looking to add additional fields that correspond to URLs for extra-outputs artifacts we produce from our analyzer task. We can generate the download URLs ourselves for these artifacts and add them as additional_info fields, but if they were made explicit then perhaps your agent could add metadata such as error information if the upload failed (for instance).

[tevoinea]

Closing because this already exists as ExtensionData