BUG: Fix Series.reindex losing values when reindexing to MultiIndex

[Roline-Stapny]

• closes #60923
• [X ] 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/v3.0.0.rst file if fixing a bug or adding a new feature.

#Before

# Create a Series with a named Index
series = pd.Series([26.73, 24.255], index=pd.Index([81, 82], name='a'))

# Create a MultiIndex with level names 'a', 'b', 'c'
target = pd.MultiIndex.from_product(
    [[81, 82], [np.nan], ["2018-06-01", "2018-07-01"]], 
    names=["a", "b", "c"]
)

# This would incorrectly set all values to NaN
series.reindex(target)
# a   b    c         
# 81  NaN  2018-06-01   NaN
#          2018-07-01   NaN
# 82  NaN  2018-06-01   NaN
#          2018-07-01   NaN

# But this works correctly
series.reindex(target, level="a")
# a   b    c         
# 81  NaN  2018-06-01    26.73
#          2018-07-01    26.73
# 82  NaN  2018-06-01    24.255
#          2018-07-01    24.255

#After

# Same setup as before
series = pd.Series([26.73, 24.255], index=pd.Index([81, 82], name='a'))
target = pd.MultiIndex.from_product(
    [[81, 82], [np.nan], ["2018-06-01", "2018-07-01"]], 
    names=["a", "b", "c"]
)

# Now both produce the same correct result
series.reindex(target)  # Automatically detects level='a'
# a   b    c         
# 81  NaN  2018-06-01    26.73
#          2018-07-01    26.73
# 82  NaN  2018-06-01    24.255
#          2018-07-01    24.255