Add implementation fields to kernel_info_reply

[bjanssen]

Fix Zed REPL: Ark kernel_info_reply was missing implementation and implementation_version fields, causing strict clients (Zed) to fail deserialization.

[github-actions]

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[DavisVaughan]

A close read of https://jupyter-client.readthedocs.io/en/latest/messaging.html#kernel-info suggests two things:

• These are indeed the 2 fields we are missing from the version 5.0 kernel_info_reply, and I have confirmed we are not missing any others

• I do not believe these fields are optional. I believe they are required. If they were optional then this would be a Zed bug IMO. So I would advocate for making them unconditionally required.

[bjanssen]

I have read the CLA Document and I hereby sign the CLA

[bjanssen]

A close read of https://jupyter-client.readthedocs.io/en/latest/messaging.html#kernel-info suggests two things:

* These are indeed the 2 fields we are missing from the version 5.0 `kernel_info_reply`, and I have confirmed we are not missing any others

* I do not believe these fields are optional. I believe they are required. If they were optional then this would be a Zed bug IMO. So I would advocate for making them unconditionally required.

I agree, removed optionality.

[DavisVaughan]

Thanks @bjanssen, we'll take it from here!