Send the .NET Runtime Identifier to Sentry

[mattjohnsonpint]

This sends the value from System.Runtime.InteropServices.RuntimeInformation.RuntimeIdentifier to Sentry with all events, on the runtime context info. This is helpful (for example) when working with MAUI events.

It shows up in the Sentry issues page under the Runtime section further down the page.

Note, that the RuntimeIdentifier property is only available on .NET 5 and greater, so it is not sent for other targets.

[mattjohnsonpint]

Per discussion, it would be nice to have it appear as a tag, like this:

But we don't want to send it as a custom tag for various reasons. Instead we'll send it just on the runtime context information, and consider having it extracted as a tag on the ingestion side.