Update specs for @import/global builtins deprecations

[jathak]

See sass/sass#3898
[skip dart-sass]
[skip sass-embedded]

[nex3]

Looks like this also needs [skip sass-embedded]

[ntkme]

The following test in importer.test.ts hasn't been updated:

  it("is converted to a file: URL if it's an absolute Windows path", () => {
    const result = compileString('@import "C:/orange";', {
      importers: [
        {
          canonicalize(url: string) {
            expect(url).toEqual('file:///C:/orange');
            return new URL(`u:${url}`);
          },
          load: () => ({contents: 'a {b: c}', syntax: 'scss'}),
        },
      ],
    });
    expect(result.css).toBe('a {\n  b: c;\n}');
  });

What's weird is that this test works with @import, but breaks with @use on ruby host. Not sure what's the intended behavior here.

From what I see this might be for some backward compatibility? As far as I know, every import used to be a path in older implementations, but now is a URI in current implementation. C:/orange is a valid path, but not a path-only RFC 3986 URI. As a URI it should be expressed as /C:/orange instead.

[nex3]

That's intended to be import-only behavior. As you surmise, it's a legacy behavior from when we were much more wishy-washy about the distinction between paths and URLs.