Add boardname grain

[nicholasmhughes]

What does this PR do?

See issue for details.

What issues does this PR fix or reference?

Fixes: #63131

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

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[nicholasmhughes]

re-run pr-centos-7-x86_64-py3-pytest

[nicholasmhughes]

re-run pr-ubuntu-2204-amd64-py3-pytest

[nicholasmhughes]

re-run pr-ubuntu-2004-amd64-py3-pytest

[lukasraska]

@nicholasmhughes what about other operating systems / architectures? Seems like the information can be retrieved from dmidecode as well, for Windows I assume https://learn.microsoft.com/en-us/windows/win32/cimwin32prov/win32-baseboard might be the correct WMI class.

For DeviceTree, the most reasonable field is model, but it's already being used for productname (https://github.com/saltstack/salt/blob/master/salt/grains/core.py#L1656 , this is for example value of model on RPi - Raspberry Pi 4 Model B Rev 1.1 ), so that could be just ignored I guess.

[Ch3LL]

@nicholasmhughes any thoughts on @lukasraska 's comment?

[nicholasmhughes]

I don't have a use case for other operating systems and I don't have any way to test them. I'd prefer to contribute this piece and allow the community to expand on it as the need arises.