add typesafe std/paths, std/files, std/dirs, std/symlinks (#20582)

* split std/os; add typesafe std/paths
* add more files, dirs, paths
* add documentation
* add testcase
* remove tryRemoveFile
* clean up
* Delete test.nim
* apply changes
* add `add` and fixes

lib/std/symlinks.nim

@@ -0,0 +1,30 @@
+from paths import Path, ReadDirEffect
+
+from std/private/ossymlinks import symlinkExists, createSymlink, expandSymlink
+
+
+proc symlinkExists*(link: Path): bool {.inline, tags: [ReadDirEffect].} =
+  ## Returns true if the symlink `link` exists. Will return true
+  ## regardless of whether the link points to a directory or file.
+  result = symlinkExists(link.string)
+
+proc createSymlink*(src, dest: Path) {.inline.} =
+  ## Create a symbolic link at `dest` which points to the item specified
+  ## by `src`. On most operating systems, will fail if a link already exists.
+  ##
+  ## .. warning:: Some OS's (such as Microsoft Windows) restrict the creation
+  ##   of symlinks to root users (administrators) or users with developer mode enabled.
+  ##
+  ## See also:
+  ## * `createHardlink proc`_
+  ## * `expandSymlink proc`_
+  createSymlink(src.string, dest.string)
+
+proc expandSymlink*(symlinkPath: Path): Path {.inline.} =
+  ## Returns a string representing the path to which the symbolic link points.
+  ##
+  ## On Windows this is a noop, `symlinkPath` is simply returned.
+  ##
+  ## See also:
+  ## * `createSymlink proc`_
+  result = Path(expandSymlink(symlinkPath.string))