Control Characters Swallowed, but only AFTER iPDB runs

IPython can accept control characters on `input`, e.g. `^_` (Control-underscore). But once iPDB is run, this is no longer possible.

```python
% ipython
Python 3.10.6 (main, Aug 30 2022, 05:12:36) [Clang 13.1.6 (clang-1316.0.21.2.5)]
Type 'copyright', 'credits' or 'license' for more information
IPython 8.5.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: input()
^_foo
Out[1]: '\x1ffoo'

In [2]: 1/0
---------------------------------------------------------------------------
ZeroDivisionError Traceback (most recent call last)
Cell In [2], line 1
----> 1 1/0

ZeroDivisionError: division by zero

In [3]: input()
^_too
Out[3]: '\x1ftoo'

In [4]: %debug
> (1)()
----> 1 1/0

ipdb> exit

In [5]: input()
# <-- can't enter control characters, rings bell. Swallows them if pasted.
```

It is convenient to be able to pass control characters to IPython processes so would be great if iPDB didn't disable this.