D5139: store: introduce _matchtrackedpath() and use it to filter store files

[Yuya Nishihara]

Can you add the following tests?

- encoded filename differs from the original name (e.g. uppercase letter)
- fncache disabled, but encodedstore is used

>      def datafiles(self, matcher=None):
>          for a, b, size in super(encodedstore, self).datafiles():
> +            if not _matchtrackedpath(a, matcher):
> +                continue
>              try:
>                  a = decodefilename(a)

I'm pretty sure it's wrong to pass in an encoded filename to matcher.