PERF: DataFrame.loc and Series.loc when key is a MultiIndex

[lukemanley]

• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/v2.2.0.rst file if fixing a bug or adding a new feature.

Avoid hitting MultiIndex.values in is_bool_indexer.

from asv_bench.benchmarks.indexing import MultiIndexing
b = MultiIndexing()
b.setup(True)
%timeit b.time_loc_multiindex(True)

# 53.3 ms ± 2.18 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)   # <- main
# 28.6 ms ± 821 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)  # <- PR

[phofl]

thx @lukemanley