[release/6.0] [release/6.0] Expand System.Runtime.InteropServices.NFloat to support the APIs required by Xamarin

[github-actions]

Backport of #64556 to release/6.0

/cc @tannergooding @github-actions[bot]

Customer Impact

Testing

Risk

[ghost]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, to please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[ghost]

Tagging subscribers to this area: @dotnet/interop-contrib
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Backport of #64556 to release/6.0

/cc @tannergooding @github-actions[bot]

Customer Impact

Testing

Risk

Author:	github-actions[bot]
Assignees:	-
Labels:	area-System.Runtime.InteropServices, new-api-needs-documentation
Milestone:	-

[tannergooding]

sigh Apparently the bot reads the relevant message anywhere in the text, not just at the begging of a line/etc and so trying to tell others the command to run triggers the bot