BUG: Can't I replace Ellipsis in DataFrame.replace like scalar

[jesrael]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

df = pd.DataFrame({'a': [1, 2, 3, 4], 'b': ['a', 'b', 'c', 'd'], 'c': [1.2, 3.4, 5.6, 7.8], 'd': [..., ..., ..., ...]})

Issue Description

Based by SO question, I cannot replace by Ellipsis:

#working 
df.mask(df == Ellipsis, 1)
df.replace(1, ...)
df.replace({Ellipsis: 1})
df .replace([...],(1))

#error
df.replace(..., 1)
df.replace(Ellipsis, 1)

TypeError: Expecting 'to_replace' to be either a scalar, array-like, dict or None, got invalid type 'ellipsis'

Expected Behavior

df =  df.replace({Ellipsis: 1})
print (df)
   a  b    c  d
0  1  a  1.2  1
1  2  b  3.4  1
2  3  c  5.6  1
3  4  d  7.8  1

Installed Versions

print (pd.show_versions())

INSTALLED VERSIONS
------------------
commit           : 2cb96529396d93b46abab7bbc73a208e708c642e
python           : 3.8.8.final.0
python-bits      : 64
OS               : Windows
OS-release       : 7
Version          : 6.1.7601
machine          : AMD64
processor        : Intel64 Family 6 Model 60 Stepping 3, GenuineIntel
byteorder        : little
LC_ALL           : None
LANG             : en
LOCALE           : sk_SK.ISO8859-2

pandas           : 1.2.4
numpy            : 1.23.1
pytz             : 2021.1
dateutil         : 2.8.1
pip              : 21.0.1
setuptools       : 52.0.0.post20210125
Cython           : 0.29.23
pytest           : 6.2.3
hypothesis       : None
sphinx           : 4.0.1
blosc            : None
feather          : None
xlsxwriter       : 1.3.8
lxml.etree       : 4.6.3
html5lib         : 1.1
pymysql          : None
psycopg2         : None
jinja2           : 2.11.3
IPython          : 7.22.0
pandas_datareader: 0.10.0
bs4              : 4.9.3
bottleneck       : 1.3.2
fsspec           : 0.9.0
fastparquet      : None
gcsfs            : None
matplotlib       : 3.3.4
numexpr          : 2.7.3
odfpy            : None
openpyxl         : 3.0.7
pandas_gbq       : None
pyarrow          : None
pyxlsb           : None
s3fs             : None
scipy            : 1.6.2
sqlalchemy       : 1.4.7
tables           : 3.6.1
tabulate         : None
xarray           : None
xlrd             : 2.0.1
xlwt             : 1.3.0
numba            : 0.53.1
None

[jessica-writes-code]

This bug seems to be occurring at (roughly) L7016 of pandas/core/generic.py, https://github.com/pandas-dev/pandas/blob/main/pandas/core/generic.py#L7016 . It seems to occur primarily because pandas/core/dtypes/inference.py:is_scalar doesn't recognize anything of type ellipsis as a scalar (i.e., when passed something of the ellipsis type, is_scalar returns False).

The -- kind of hacky? -- fix of including to_replace is Ellipsis as one of the or-ed conditions does appear to work. A more elegant fix seems to require editing something much lower-level. If the former is acceptable, I'm happy to open a PR with that change.