refactor(fs): use every instead of reduce (#5323)

The previous usage of `reduce` was basically implementing the `every`

A small difference is that the new implementation will stop checking 
as soon as one element have returned false, which will reduce 
the number of unnecessary checks.

std/fs/_util.ts

@@ -16,11 +16,7 @@ export function isSubdir(
   }
   const srcArray = src.split(sep);
   const destArray = dest.split(sep);
-  // see: https://github.com/Microsoft/TypeScript/issues/30821
-  // @ts-ignore
-  return srcArray.reduce((acc: true, current: string, i: number): boolean => {
-    return acc && destArray[i] === current;
-  }, true);
+  return srcArray.every((current, i) => destArray[i] === current);
 }
 
 export type PathType = "file" | "dir" | "symlink";