Class types with layout that inherit from System.Object should be ManagedSequential

[jkoritzinsky]

Fixes #65412

[AaronRobinsonMSFT]

Let's get a test for this. I would have thought we had one already. I'd like to ensure we have testing for all four of the below:

[StructLayout(LayoutKind.Sequential)]
class BaseSeq {}

class Derived : BaseSeq {}

class BaseAuto {}

[StructLayout(LayoutKind.Sequential)]
class Derived : BaseAuto {}

[jkoritzinsky]

The test suites that failed here were deadlettered (probably due to capacity issues). Merging this in.

[jkoritzinsky]

/backport to release/7.0-preview2

[github-actions]

Started backporting to release/7.0-preview2: https://github.com/dotnet/runtime/actions/runs/1865996343