BUG, TST: Patch handling of uint64 in algorithms
1) Patches handling of `uint64` in `value_counts`
2) Adds tests for handling of `uint64` in `factorize`

xref #14934
## [Current coverage](https://codecov.io/gh/pandas-dev/pandas/pull/15162?src=pr) is 85.68% (diff: 100%)
> Merging [#15162](https://codecov.io/gh/pandas-dev/pandas/pull/15162?src=pr) into [master](https://codecov.io/gh/pandas-dev/pandas/branch/master?src=pr) will increase coverage by **<.01%**

```diff
@@             master     #15162   diff @@
==========================================
  Files           145        145          
  Lines         51419      51427     +8   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          44057      44066     +9   
+ Misses         7362       7361     -1   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [97fd744...1fb256b](https://codecov.io/gh/pandas-dev/pandas/compare/97fd7447ff54d8f964d057dbaad2b5caa362e24d...1fb256be46a35d80d05edaa82cafee8c164adb58?src=pr) this looks pretty good. prob some cases to care about after though. ping when updated tests as above. thanks @gfyoung !