REF/PERF: MultiIndex.get_indexer with method

[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.

from asv_bench.benchmarks.multiindex_object import Integer

b = Integer()
b.setup()

%timeit b.time_get_indexer_and_backfill()

# 238 ms ± 39.6 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)     -> main
# 50.6 ms ± 2.98 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)  -> PR

%timeit b.time_get_indexer_and_pad()

# 191 ms ± 30.3 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)   -> main
# 50.4 ms ± 1.03 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)  -> PR

[WillAyd]

Nice! Always great to improve performance while reducing code.

A cursory glance tells me the failures are unrelated but worth merging main to be sure

[mroeschke]

Thanks @lukemanley (yeah these failures are not related)