We should call out to the embedder to resolve native assets and symbols.

This would enable the embedder resolving symlinks:

• [native_assets] Relative path resolution with symlinks #55410
• [native-assets] Windows lookup fails when exe is symlinked #55207

Also it would enable the embedder not having the files on disk at all or having the as part of a larger file and using dlopen_with_offset.

The embedder would provide an API for dlopen(), dlclose(), dlsym(), dladdr().

The embedder API would be tied to the new native assets feature. So dlopen would take a native assets mapping such as ['relative', 'some/file/path.so'] or ['process']. (As such it would not be used for DynamicLibrary.open and DynamicLibrary.lookup. #37771)

Having a dlclose embedder callback is only useful when we unload dynamic libraries on isolate group shutdown:

• [vm/ffi] Native asset dynamic libraries should be dlclosed on isolate (group) shutdown #55521

Having a dladdr embedder callback is only if we add some functionality that uses this. We currently don't have such functionality.