CLN: move tools.hashing to util.hashing
xref https://github.com/pandas-dev/pandas/issues/13634
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16086?src=pr&el=h1) Report
> Merging [#16086](https://codecov.io/gh/pandas-dev/pandas/pull/16086?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1f16ca7a821b705010197c37b529f494060888c3?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16086/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/16086?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #16086   +/-   ##
=======================================
  Coverage   90.84%   90.84%           
=======================================
  Files         159      159           
  Lines       50790    50790           
=======================================
  Hits        46142    46142           
  Misses       4648     4648
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.62% <100%> (ø)` | :arrow_up: |
| #single | `40.36% <100%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16086?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/hashing.py](https://codecov.io/gh/pandas-dev/pandas/pull/16086?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvaGFzaGluZy5weQ==) | `99.02% <100%> (ø)` | |
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/16086?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `96.71% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16086?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16086?src=pr&el=footer). Last update [1f16ca7...d0acb0c](https://codecov.io/gh/pandas-dev/pandas/pull/16086?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 cc @mrocklin

FYI thanks @jorisvandenbossche 