Add Zero and IsZero properties to Quaternion.

[Takym]

This pull request resolves #57253.

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Issue Details

---

This pull request resolves #57253.

Author:	Takym
Assignees:	-
Labels:	area-System.Numerics
Milestone:	-

[GrabYourPitchforks]

Hi @Takym! Thanks for the PR. Unfortunately the original issue is not yet marked api-approved, so we can't accept this PR at this time. See https://github.com/dotnet/runtime/blob/main/docs/project/api-review-process.md#pull-requests for more information on the API approval process and the timelines for when PRs are accepted.

[Takym]

Hello @GrabYourPitchforks! Thank you for replying. Do I need to re-create a PR when the original issue is marked as api-approved, or will you reopen this PR?

[GrabYourPitchforks]

I think you have the power to reopen the PR yourself at the right time. If not, leave a comment here and somebody should be able to reopen it on your behalf. The system won't auto-lock the issue for quite some time.

[Takym]

I clearly understood. Thanks.

[Takym]

Would you please reopen this PR because the issue was marked as api-approved?

[GrabYourPitchforks]

@Takym Reopening. Only the Zero property was approved in API review; there didn't seem to be much love for an IsZero property.

Don't forget to update the ref assemblies and provide unit tests for the new API while you're at it. :)

Edit: Looks like you already beat me to the unit tests!

[Takym]

I added property definitions to the reference assembly in 7a54468.

Also, I have created a "no IsZero" version below:
Takym/runtime@Quaternion...Quaternion2

[stephentoub]

This can be closed now that #58406 has been opened, yes?

[Takym]

@stephentoub Yes.