BUG: astype ignore errors not working for categorical/StringArray
- [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.

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

---

#### Problem description

It seems to be ignoring `errors='ignore'` kwarg. The behavior in 0.25.3 is expected.

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

```python
import pandas as pd
pd.__version__
# '1.0.5'

pd.Series(pd.Categorical(['A', 'B'])).astype(float, errors='ignore')
# ---------------------------------------------------------------------------
# ValueError                                Traceback (most recent call last)
# <ipython-input-4-3d39cd9c1cdd> in <module>
# ----> 1 pd.Series(pd.Categorical(['A', 'B'])).astype(float, errors='ignore')
#
# ...
# ValueError: could not convert string to float: 'A'
```


#### Expected Output


```python
import pandas as pd
pd.__version__
# '0.25.3'

pd.Series(pd.Categorical(['A', 'B'])).astype(float, errors='ignore')
# 0    A
# 1    B
# dtype: category
# Categories (2, object): [A, B]
```

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

<details>

INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.7.final.0
python-bits      : 64
OS               : Linux
OS-release       : 3.10.0-1062.4.1.el7.x86_64
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 1.0.5
numpy            : 1.18.5
pytz             : 2020.1
dateutil         : 2.8.1
pip              : 20.1.1
setuptools       : 49.2.0.post20200714
Cython           : None
pytest           : 6.0.0
hypothesis       : None
sphinx           : 3.1.2
blosc            : None
feather          : None
xlsxwriter       : 1.2.9
lxml.etree       : 4.5.2
html5lib         : None
pymysql          : None
psycopg2         : 2.8.5 (dt dec pq3 ext lo64)
jinja2           : 2.11.2
IPython          : 7.16.1
pandas_datareader: None
bs4              : None
bottleneck       : 1.3.2
fastparquet      : 0.3.2
gcsfs            : None
lxml.etree       : 4.5.2
matplotlib       : 3.2.2
numexpr          : 2.7.1
odfpy            : None
openpyxl         : 3.0.4
pandas_gbq       : None
pyarrow          : 0.15.1
pytables         : None
pytest           : 6.0.0
pyxlsb           : None
s3fs             : None
scipy            : 1.3.1
sqlalchemy       : 1.3.18
tables           : None
tabulate         : 0.8.7
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : 1.2.9
numba            : 0.50.1
</details>
