lib: make sure globals can be loaded after globalThis is sealed
Since we made some of the globals lazily loaded to reduce startup overhead, and tried to update then as data properties once loaded, the lazily-loaded globals can no longer be loaded once globalThis is freezed. Fix this by not attempting to overwrite the property on loading these globals (so the property descriptors won't be spec-compliant in this case, but at least it's a good compromise between breakages and startup overhead).
Note that certain globals that come from undici are still broken because undici attempts to define a global dispatcher symbol on globalThis. This is reflected in the test.