[wasm coreclr] Fix fields alignment (#115364)

* Fix fields alignment

Fixes #115363

The problem happened in MethodTableBuilder::PlaceInstanceFields where in wasm case
the fields were placed at wrong offsets.

The native representation looks like this:

```
class  field                                        wasm type          offset
-----------------------------------------------------------------------------------------------
Object
       PTR_MethodTable m_pMethTab                   i32                0
AssemblyLoadContextBaseObject
       int64_t         _id                          i64                8
       OBJECTREF       _unloadLock                  i32                12
       OBJECTREF       _resolvingUnmanagedDll       i32
       OBJECTREF       _resolving                   i32
       OBJECTREF       _unloading                   i32
       OBJECTREF       _name                        i32
       INT_PTR         _nativeAssemblyLoadContext   i32
       DWORD           _state                       i32                40
       CLR_BOOL        _isCollectible               i8                 44
```

While the managed field offsets were calculated wrong, the _id was
placed at offset 4 and thus all the following fields were at wrong
offsets too. The size check then failed.

By enabling FEATURE_64BIT_ALIGNMENT the dwOffsetBias is set to
TARGET_POINTER_SIZE and the fields layout is calculated properly.

The 8 bytes types in wasm should be aligned to 8 bytes

https://github.com/WebAssembly/tool-conventions/blob/main/BasicCABI.md#data-representation

so hopefully the rest of the changes enabled by this feature should
apply as well. Before this feature was enabled only for arm 32bits.

* Update conditions to use TARGET_WASM

* Apply suggestions from code review

* Apply suggestions from code review

---------

Co-authored-by: Jan Kotas <[email protected]>

Author: radekdoulik

src/coreclr/gc/env/gcenv.object.h

@@ -8,10 +8,8 @@
 extern bool g_oldMethodTableFlags;
 #endif
 
-// ARM requires that 64-bit primitive types are aligned at 64-bit boundaries for interlocked-like operations.
-// Additionally the platform ABI requires these types and composite type containing them to be similarly
-// aligned when passed as arguments.
-#ifdef TARGET_ARM
+// Some 32-bit platform ABIs require that 64-bit primitive types and composite types containing them are aligned at 64-bit boundaries.
+#if defined(TARGET_ARM) || defined(TARGET_WASM)
 #define FEATURE_64BIT_ALIGNMENT
 #endif
 

src/coreclr/inc/switches.h

@@ -146,10 +146,8 @@
 #define FEATURE_HFA
 #endif
 
-// ARM requires that 64-bit primitive types are aligned at 64-bit boundaries for interlocked-like operations.
-// Additionally the platform ABI requires these types and composite type containing them to be similarly
-// aligned when passed as arguments.
-#ifdef TARGET_ARM
+// Some 32-bit platform ABIs require that 64-bit primitive types and composite types containing them are aligned at 64-bit boundaries.
+#if defined(TARGET_ARM) || defined(TARGET_WASM)
 #define FEATURE_64BIT_ALIGNMENT
 #endif