Linker appears to incorrectly trim static field initialization logic

The following simple program fails with a segmentation fault:
```xml

Exe
net6.0
false

```

```csharp
using System;

namespace ConsoleApp7
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine(DateTime.Now);
}
}
}
```

```sh
$ dotnet publish -c Release -r linux-x64 -p:PublishTrimmed=true -p:TrimMode=link
$ ./bin/Release/net6.0/linux-x64/publish/ConsoleApp7
Segmentation fault (core dumped)
```

This appears to be because `System.Globalization.GlobalizationMode` is trimmed down to just the following:
```csharp
namespace System.Globalization
{
internal static class GlobalizationMode
{
internal static bool Invariant => false;

internal static bool UseNls => false;
}
}
```

The original file is here: https://source.dot.net/#System.Private.CoreLib/GlobalizationMode.Unix.cs,f6b65aaea1440971

As you can see, the `Invariant` property has a field initializer which is getting trimmed where it should not be as it has necessary side effects. My guess is that the backing field that gets generated for such logic is getting trimmed because it is private and not returned anywhere: (https://sharplab.io/#v2:EYLgxg9gTgpgtADwGwBYA0ATEBqAPgAQCYBGAWACh8BmAAn2KTsJoGEaBvCm7mgSwDsALjCj8AhgBs6DGsAgQpASX4A3MVF5ihHGgHMYggNw0AvjQC8NAOIGrEiMEm8AXmMG8I/ZWo1bBAWQgMGAAKAEpDLh5oqO4ABw01YWlGOQVrW3tHCRc3Dy9VdU0hQODw2I4K6PwAdhoAM0kAZxhI8miTChMgA=)