Support for CloudEvents SQL (CESQL)

[thern743]

The CESQL v1.0 spec has been out since July 2024. C# should follow other languages like Goland and Java in supporting this spec:

https://cloudevents.io/blog/2024-07-15/

[jskeet]

I think it's unlikely that we'll ever do that - I'd review a PR, but that's the limit of what my personal involvement would be.

The C# SDK is mostly for consuming and producing CloudEvents, not hosting servers around them - which is what an implementation would presumably be about.