First steps towards x86 compatible crossgen2 (#42471)

First steps towards x86 compatible crossgen2 (#42471)

- Fix bug in crossgen2 around compilation of type forwarder only assemblies
- Use 64bit x86 crossgen2 when running crossgen2 as part of test build
- Disable inlined pinvoke generation on X86 until failures are understood
- Autolayout alignment should align to 4 byte offsets on X86 platforms
- Convert ArgIterator to use CoreCLR ABI instead of ProjectN ABI
- Align instance fields of classes to the start of the fields of the object, not the start of the object
- Fix hardware intrinsic support for X86
- MDArray address method uses custom calling convention on X86
- X86 JIT expects VM to normalize some single element structures to int, and inptr types
- Enable crossgen2smoke test for x86

With this change the crossgen2smoke test passes when compiled with crossgen2, as do simpler tests which use a crossgen2 compiled variant of the framework libraries. crossgen2smoke + libraries compiled with crossgen2 does not pass due to issues in resource handling.