Don't require AppHost when publishing AOT

[MichalStrehovsky]

We only delete it anyway.

Contributes to dotnet/runtime#89763
Contributes to dotnet/runtime#79575

_RuntimeIdentifierUsesAppHost is not a great name for this but I need exactly the same sematic. Renaming the existing property is not an option because there's external dependencies on this.

Cc @dotnet/ilc-contrib @rolfbjarne @ViktorHofer

[ViktorHofer]

I just saw @jkotas's comment in the other issue:

We do want to keep using app host for dotnet run or F5 in Visual Studio. I do not think we want to change the global default to false when PublishAot is set.

[MichalStrehovsky]

I just saw @jkotas's comment in the other issue:

We do want to keep using app host for dotnet run or F5 in Visual Studio. I do not think we want to change the global default to false when PublishAot is set.

That's what the '$(_IsPublishing)' == 'true' part is guarding.

[ilonatommy]

/backport to release/8.0.4xx

[github-actions]

Started backporting to release/8.0.4xx: https://github.com/dotnet/sdk/actions/runs/10177576653

[ilonatommy]

/backport to release/8.0.1xx

[github-actions]

Started backporting to release/8.0.1xx: https://github.com/dotnet/sdk/actions/runs/10177871330