fix: normalize playlist:validate file arguments

playlist:validate decides which streams belong to the selected files by
comparing the raw command-line arguments with the paths returned by
Storage.list(). A path such as ./streams/us.m3u never matches
streams/us.m3u, so the file's own streams are put in the duplicate buffer
and every link is reported as already being in that same file.

Resolve the arguments with getStoragePath(), as playlist:format does.

tests/__data__/input/playlist_validate_paths/streams/example.m3u

@@ -0,0 +1,3 @@
+#EXTM3U
+#EXTINF:-1 tvg-id="",Example (720p)
+https://example.com/playlist.m3u8