[bun dev] Automatically set origin - improve support for proxying Bun

Previously, when running Bun behind a reverse proxy, you had to pass an explicit `--origin` arg and it could only run behind one proxy at a time.

Now, Bun automatically determines the origin from the request if possible. It reads `Forwarded`, `X-Forwarded-Proto`, `X-Forwarded-Host`, `Origin`, and lastly `Host`. If none are available, it falls back to the `--origin` CLI arg.

This change is important for usecases like Replit which shows multiple iframes in different origins.

src/javascript/jsc/api/router.zig

@@ -390,11 +390,12 @@ pub fn getScriptSrcString(
                 &entry_point_tempbuf,
                 Fs.PathName.init(file_path),
             ),
+            VirtualMachine.vm.origin,
             ScriptSrcStream.Writer,
             writer,
         );
     } else {
-        JavaScript.Bun.getPublicPath(file_path, ScriptSrcStream.Writer, writer);
+        JavaScript.Bun.getPublicPath(file_path, VirtualMachine.vm.origin, ScriptSrcStream.Writer, writer);
     }
 }