tm.assert_series_equal checking on Integer EA should be exact by default?

#### Code Sample, a copy-pastable example if possible

```python
>>>
>>> import pandas as pd
>>> pd.__version__
'0.26.0.dev0+1328.g03dffb1eb'
>>>
>>> import pandas.testing as tm
>>> s1 = pd.Series([10000000000000000], dtype="Int64")
>>> s1
0    10000000000000000
dtype: Int64
>>>
>>> s2 = pd.Series([9999999999999999], dtype="Int64")
>>> s2
0    9999999999999999
dtype: Int64
>>>
>>> tm.assert_series_equal(s1,s2)
>>>
```
#### Problem description

does not raise

#### Expected Output

`AssertionError: ExtensionArray are different`

#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit           : 03dffb1eb312d1bc535e26f43e32c11e0584c8c5
python           : 3.7.3.final.0
python-bits      : 64
OS               : Windows
OS-release       : 10
machine          : AMD64
processor        : Intel64 Family 6 Model 69 Stepping 1, GenuineIntel
byteorder        : little
LC_ALL           : None
LANG             : en_GB.UTF-8
LOCALE           : None.None

pandas           : 0.26.0.dev0+1328.g03dffb1eb
numpy            : 1.17.3
pytz             : 2019.3
dateutil         : 2.8.0
pip              : 19.3.1
setuptools       : 42.0.2.post20191201
Cython           : 0.29.14
pytest           : 5.3.2
hypothesis       : 4.54.1
sphinx           : 2.3.0
blosc            : None
feather          : None
xlsxwriter       : 1.2.6
lxml.etree       : 4.4.2
html5lib         : 1.0.1
pymysql          : None
psycopg2         : None
jinja2           : 2.10.3
IPython          : 7.10.2
pandas_datareader: None
bs4              : 4.8.1
bottleneck       : 1.3.1
fastparquet      : 0.3.2
gcsfs            : None
lxml.etree       : 4.4.2
matplotlib       : 3.1.2
numexpr          : 2.7.0
odfpy            : None
openpyxl         : 3.0.1
pandas_gbq       : None
pyarrow          : 0.15.1
pytables         : None
pytest           : 5.3.2
s3fs             : 0.4.0
scipy            : 1.3.1
sqlalchemy       : 1.3.11
tables           : 3.6.1
xarray           : 0.14.1
xlrd             : 1.2.0
xlwt             : 1.3.0
xlsxwriter       : 1.2.6

</details>

discovered while investigating #30268