BUG/PERF: use lexsort_indexer in MultiIndex.argsort
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cc: @phofl, @mroeschke - follow on to #48406

Had I been aware of lexsort_indexer I would have used that in #48406. Using lexsort_indexer handles `pd.NA` (np.lexsort raises) and has better perf for nullable types (Int64 on par with int64).

While the perf for non-nullable types (e.g. int64) suffers a bit, this is still much faster than prior to #48406. 

```
       before           after         ratio
     [4e72340d]       [ead3c00d]
     <main>           <multiindex-argsort>
+     1.78±0.03ms       3.59±0.4ms     2.01  multiindex_object.SortValues.time_sort_values('int64')
-      26.7±0.5ms       3.51±0.5ms     0.13  multiindex_object.SortValues.time_sort_values('Int64')
``` 
> Special casing only numpy dtypes makes it ugly, correct?

That was my thinking. DataFrame.sort_index uses the same approach with lexsort_indexer and does not special case numpy dtypes. Ok, sounds reasonable Can you merge main to get ci green? > Would be good to have a test that calls `MultiIndex.argsort` directly

added an explicit argsort test Just merged the other pr. Could you maybe run asvs once more? Union has a bunch of code paths, want to see if this is affected  > Just merged the other pr. Could you maybe run asvs once more? Union has a bunch of code paths, want to see if this is affected

I don’t think this touches union. Were you thinking of #48504 ? @phofl, @mroeschke 

This is now failing following the merge of #48505. The test failing is `test_union_sort_other_incomparable` which expects to see a RunTimeWarning from `MultiIndex._union`. However, this uncovers some inconsistency in the main branch.

Here is an example:

```
import pandas as pd
idx = pd.MultiIndex.from_product([[pd.Timestamp("2000"), 1], ["a", "b"]])
df = pd.DataFrame({"A": 1}, index=idx)

# on main, this returns without warning/error as it goes through lexsort_indexer
df.sort_index()

# on main, this raises a TypeError as it goes through np.lexsort
df.index.sort_values()
```

With this PR the behavior will be consistent as we'll be sending both through lexsort_indexer. I've removed the expectation for a RunTimeWarning from the test. Let me know if that doesn't make sense.  @phofl - gentle ping. I think this is ready. thx. @lukemanley 