BUG: ExtensionArrays whose elements are non-numeric numpy arrays crash Series.__repr__()
- [X] I have checked that this issue has not already been reported.

- [X] I have confirmed this bug exists on the latest version of pandas.

- [X] (optional) I have confirmed this bug exists on the master branch of pandas.

---

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

Prerequisites:
```console
$ pip install pandas numpy memoized-property
$ pip install git+https://github.com/frreiss/text-extensions-for-pandas
```

Reproduce the problem, using [`TensorArray`](https://github.com/frreiss/text-extensions-for-pandas/blob/master/text_extensions_for_pandas/array/tensor.py), our extension type for storing tensors in a Pandas series:
```python
>>> import pandas as pd
>>> import numpy as np
>>> import text_extensions_for_pandas as tp
>>> # Integers work
    int_tensors = np.array([[1, 2], [3, 4]])
    int_tensor_series = pd.Series(tp.TensorArray(int_tensors))
    int_tensor_series

0   [1 2]
1   [3 4]
dtype: TensorType

>>> # Boolean values don't work
    bool_tensors = np.array([[True, False], [False, True]])
    bool_tensor_series = pd.Series(tp.TensorArray(bool_tensors))
    bool_tensor_series
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
~/pd/covid-notebooks/env/lib/python3.7/site-packages/IPython/core/formatters.py in __call__(self, obj)
    700                 type_pprinters=self.type_printers,
    701                 deferred_pprinters=self.deferred_printers)
--> 702             printer.pretty(obj)
    703             printer.flush()
    704             return stream.getvalue()

[...many lines of stack trace...]

~/pd/covid-notebooks/env/lib/python3.7/site-packages/pandas/io/formats/format.py in _format_strings(self)
   1255         fmt_values = []
   1256         for i, v in enumerate(vals):
-> 1257             if not is_float_type[i] and leading_space:
   1258                 fmt_values.append(" {v}".format(v=_format(v)))
   1259             elif is_float_type[i]:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

```

#### Problem description

`Series.__repr__()` invokes `ExtensionArrayFormatter` to render extension types. If the individual elements managed by an ExtensionArray are numpy arrays (or slices of a larger numpy array), then  `ExtensionArrayFormatter` uses Pandas' facilities for rendering numpy arrays. These facilities comprise the base class `GenericArrayFormatter` and subclasses such as `FloatArrayFormatter` for handling specific types (see `pandas/io/formats/format.py`). The formatters for numeric types can render numpy arrays with more than one dimension, but the base class `GenericArrayFormatter` cannot. The limitation appears to be an oversight. I will submit a small pull request with a fix in a few minutes.

#### Expected Output

The above code should output something like this:

```python
0   [True False]
1   [False True]
dtype: TensorType
```

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

<details>

INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.7.final.0
python-bits      : 64
OS               : Darwin
OS-release       : 19.4.0
machine          : x86_64
processor        : i386
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 1.0.3
numpy            : 1.18.1
pytz             : 2019.3
dateutil         : 2.8.1
pip              : 20.0.2
setuptools       : 46.1.3.post20200330
Cython           : 0.29.15
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : 2.11.1
IPython          : 7.13.0
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : 0.3.3
gcsfs            : None
lxml.etree       : None
matplotlib       : 3.1.3
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : 0.13.0
pytables         : None
pytest           : None
pyxlsb           : None
s3fs             : None
scipy            : 1.4.1
sqlalchemy       : None
tables           : None
tabulate         : 0.8.3
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None
numba            : 0.49.0

</details>
