v0.0.8: use github.com/charlievieth/fastwalk for 10x speedup

commit 506ca26
Author: Charlie Vieth charlie.vieth@gmail.com
Date: Sun Aug 7 17:37:01 2022 -0400

pkgs: use github.com/charlievieth/fastwalk for 10x speedup

This commit changes pkgs to use github.com/charlievieth/fastwalk
for a 10x speedup and adds tests.

```
name       old time/op    new time/op    delta
Import-10     866ms ±11%      85ms ± 3%  -90.13%  (p=0.008 n=5+5)

name       old alloc/op   new alloc/op   delta
Import-10    8.72MB ± 2%   11.57MB ± 1%  +32.61%  (p=0.008 n=5+5)

name       old allocs/op  new allocs/op  delta
Import-10      122k ± 0%      136k ± 0%  +11.12%  (p=0.008 n=5+5)
```