Update NJsonSchema to v11

[NoahStolk]

(Original PR: #2185)

Fixes #2169

A few notes:

• This is a breaking change, and should be included in a major version release only, as we're dropping support for NJsonSchema v10. This change will impact users that manage their own references to NJsonSchema v10.
• Newtonsoft.Json-based generators have been moved to a separate NuGet package, so the reference to NJsonSchema has been replaced with a reference to NJsonSchema.NewtonsoftJson. See NSwag 14 announcement and NJsonSchema v11 release notes.
• EnumHandling no longer exists, so the WithJsonSchemaGeneratorSettingsSerDe unit test has been updated to use JsonSerializerSettings instead.

[cla-assistant]

All committers have signed the CLA.

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

Noah Stolk seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[rayokota]

Thanks @NoahStolk , LGTM

[rayokota]

@NoahStolk , I intend to merge this PR, and then we can figure out a subsequent PR to figure out how best to minimize breaking backward compatibility. Unfortunately I can't merge at the moment as we're doing some internal work to change the protection rules for public repos.

[rayokota]

@NoahStolk , just an FYI that we don't have an ETA for when the protection rules will be fixed (hopefully in a few weeks), but I won't forget about this PR.

[NoahStolk]

Thanks @rayokota, do you plan to merge this PR as is, and then add the NET8_0_OR_GREATER directives? Or should they be included in this branch before the merge?

[rayokota]

If you want to add it to this PR, that would be great. Otherwise we could add it to a subsequent PR

[rayokota]

@NoahStolk , on second thought, can you take a look at adding the directives to this PR? So that we don't break users in case we need to cut a patch release from master. Thanks!

[NoahStolk]

Will try to find some time to do that this week.

[rayokota]

Thanks @NoahStolk , LGTM

[NoahStolk]

Thanks @rayokota

FYI: Not all (.NET 8) unit tests are passing yet, I'm getting some of these errors.

Any ideas? If not I'll debug some time later. Haven't had a lot of time to look into this yet.

I also don't have .NET 6 installed anymore, so I don't know if the old tests are still passing.

I had another question... Do we need to multi-target the JsonWithReferences and Confluent.SchemaRegistry.Serdes.IntegrationTests projects? I just upgraded them to .NET 8.

[rayokota]

Thanks @NoahStolk , I believe the .NET 6 tests are still passing. Yeah, I'm not sure about the .NET 8 ones. Let me know if you can't figure it out and maybe I can take a look as well.

[rayokota]

Thanks @NoahStolk. The issue is RicoSuter/NJsonSchema#1696. I'll merge this PR and fix the tests in a subsequent PR.

[NoahStolk]

Thank you!