TST: Avoid hashing np.timedelta64 without unit
Avoids

```bash
____________________ TestValueCounts.test_value_counts_nat _____________________
[gw3] linux -- Python 3.13.0 /opt/hostedtoolcache/Python/3.13.0/x64/bin/python

self = <pandas.tests.test_algos.TestValueCounts object at 0x7f7c3f35dd20>

    def test_value_counts_nat(self):
        td = Series([np.timedelta64(10000), NaT], dtype="timedelta64[ns]")
        dt = to_datetime(["NaT", "2014-01-01"])
    
        for ser in [td, dt]:
            vc = algos.value_counts_internal(ser)
            vc_with_na = algos.value_counts_internal(ser, dropna=False)
            assert len(vc) == 1
            assert len(vc_with_na) == 2
    
        exp_dt = Series({Timestamp("2014-01-01 00:00:00"): 1}, name="count")
        result_dt = algos.value_counts_internal(dt)
        tm.assert_series_equal(result_dt, exp_dt)
    
>       exp_td = Series({np.timedelta64(10000): 1}, name="count")
E       ValueError: Can't hash generic timedelta64

pandas/tests/test_algos.py:1257: ValueError
```
Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

```
git checkout 2.3.x
git pull
```

2. Cherry pick the first parent branch of the this PR on top of the older branch:
```
git cherry-pick -x -m1 0b6cece3acda1ae6e4f582d8276851b02aeac1ea
```

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

```
git commit -am 'Backport PR #60416: TST: Avoid hashing np.timedelta64 without unit'
```

4. Push to a named branch:

```
git push YOURFORK 2.3.x:auto-backport-of-pr-60416-on-2.3.x
```

5. Create a PR against branch 2.3.x, I would have named this PR:

> "Backport PR #60416 on branch 2.3.x (TST: Avoid hashing np.timedelta64 without unit)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the `Still Needs Manual Backport` label once the PR gets merged.

If these instructions are inaccurate, feel free to [suggest an improvement](https://github.com/MeeseeksBox/MeeseeksDev).
                