BUG: 35977 Adding regex support for ExtensionBlock replace method
- [x] closes #35977 
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Overrides replace method to add support of regex in ExtensionBlock . If input to_replace is a regex we convert data type of block to Object and calls object replace method which supports regex otherwise we call replace method of super class Block.

```ipython
In [2]: b.replace(r'^\s*$', pd.NA, regex=True, inplace=True)
   ...: print(b)
   a     b
0  a     d
1  b  <NA>
2  c  <NA>

In [3]: b.replace(r'^\s*$', pd.NA, regex=True, inplace=False)
Out[3]: 
   a     b
0  a     d
1  b  <NA>
2  c  <NA>


```