Allow annotating top-level or static fields with `@Native` to create
fields backed by native memory.
By using the `_addressOf` operator implemented in the VM, these fields
can be implemented in the CFE by replacing them with accessors looking
up the pointer and then using existing methods to load and store the
value.
Closes https://github.com/dart-lang/sdk/issues/50551
TEST=tests/ffi/native_assets/asset_*_test.dart
TEST=pkg/analyzer/test/src/diagnostics/ffi_native_test.dart
CoreLibraryReviewExempt: VM & dart2wasm only feature
Change-Id: I61dccc88076723d6a6ba02d7fd848b18e4caf780
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/338020
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Lasse Nielsen <lrn@google.com>
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>
Simon Binder
150e61a662