`RuntimeInformation.ProcessArchitecture` returns X64 architecture for Arm64 tests

### .NET version

7.0

### Did it work in .NET Framework?

No

### Did it work in any of the earlier releases of .NET Core or .NET 5+?

_No response_

### Issue description

Tests are run for x86, x64 and arm64 architectures. Some tests could be flaky on a specific architecture, so we introduced an attribute to skip a test when run on a certain architecture (https://github.com/dotnet/winforms/pull/6599). The attribute uses the `System.Runtime.InteropServices.RuntimeInformation.ProcessArchitecture` property to determine the architecture. However, this property returns `Architecture.X64` for arm64 tests, which makes skipping tests for arm64 not working as expected.

For example, while `DataGridViewTests.DataGridView_ColumnHeadersHeight_SetWithHandle_GetReturnsExpected` has following attribute:
```
[ConditionalWinFormsTheory(UnsupportedArchitecture = Architecture.Arm64,
Skip = "Flaky tests, see: https://github.com/dotnet/winforms/issues/6597")]
```
it is still executed on arm64:

### Steps to reproduce

1. Add Arm64 as an unsupported architecture on a unit test.
2. Search for the test in CI pipeline test results.