PERF: MultiIndex.values for MI's with DatetimeIndex, TimedeltaIndex, or ExtensionDtype levels

[lukemanley]

• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added an entry in the latest doc/source/whatsnew/v1.5.0.rst file if fixing a bug or adding a new feature.

The change is to do the boxing of these types on the distinct level values and then call .take rather than calling .take and then having to box a potentially much larger array.

The impact is most pronounced when there is a large difference between the number of rows in the index and the number of unique values (e.g. dates) in a given level of the index.

import pandas as pd
import numpy as np

mi = pd.MultiIndex.from_product(
    [ 
        pd.array(np.arange(10000), dtype="Int64"),
        pd.date_range('2000-01-01', periods=1000),
    ]
)

%timeit mi.copy().values

6.63 s ± 212 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)   <- main
775 ms ± 6.99 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)  <- PR

Existing asvs:

$ asv continuous -f 1.1 upstream/main multiindex-values -b multiindex_object

       before           after         ratio
     <main>           <multiindex-values>
-        32.0±2ms       28.6±0.3ms     0.89  multiindex_object.Duplicated.time_duplicated
-         215±3ms          151±5ms     0.70  multiindex_object.SetOperations.time_operation('non_monotonic', 'datetime', 'intersection')
-       347±0.8ms          226±3ms     0.65  multiindex_object.SetOperations.time_operation('monotonic', 'datetime', 'intersection')
-         323±3ms          208±2ms     0.64  multiindex_object.SetOperations.time_operation('monotonic', 'datetime', 'union')
-         326±5ms          207±5ms     0.64  multiindex_object.SetOperations.time_operation('non_monotonic', 'datetime', 'union')
-         139±1ms         32.4±2ms     0.23  multiindex_object.SetOperations.time_operation('monotonic', 'datetime', 'symmetric_difference')
-         140±2ms       32.3±0.8ms     0.23  multiindex_object.SetOperations.time_operation('non_monotonic', 'datetime', 'symmetric_difference')
-        65.6±3ms       8.79±0.2ms     0.13  multiindex_object.Values.time_datetime_level_values_copy

[jreback]

thanks @lukemanley keep em coming!