[vm/ffi] Array.fromTypedData constructors

[dcharkes]

In [vm/ffi] TypedData constructors for Struct and Union addressing #53418, structs and unions can be instantiated with an existing typed data.

We should consider doing the same for Array.

Related:

• [vm/ffi] Struct and Union constructors fromTypedList #53418

Workaround for compile-time length arrays

After https://dart-review.googlesource.com/c/sdk/+/342763 lands.

Define a wrapper struct, create the wrapper struct with that typed data, and read the array out:

main() {
  final typedData = ...;
  final Array<MyStruct> a = HelperStruct(typedData).inlineArray;
}

class HelperStruct extends Struct {
  @Array(10)
  external Array<Struct> inlineArray;
}