If the user had `config.get("show_crash_reporter")==False`, they would
never get to see excs collected via `send_exception_to_crash_reporter(exc)`.
E.g.:
```
E | gui.qt.ElectrumGui | error loading wallet (or creating window for it)
Traceback (most recent call last):
File "/opt/electrum/electrum/gui/qt/__init__.py", line 433, in main
if not self.start_new_window(path, self.config.get('url'), app_is_starting=True):
File "/opt/electrum/electrum/gui/qt/__init__.py", line 307, in wrapper
return func(self, *args, **kwargs)
File "/opt/electrum/electrum/gui/qt/__init__.py", line 332, in start_new_window
wallet = self._start_wizard_to_select_or_create_wallet(path)
File "/opt/electrum/electrum/gui/qt/__init__.py", line 377, in _start_wizard_to_select_or_create_wallet
db = WalletDB(storage.read(), manual_upgrades=False)
File "/opt/electrum/electrum/wallet_db.py", line 73, in __init__
self.load_data(raw)
File "/opt/electrum/electrum/wallet_db.py", line 104, in load_data
self._after_upgrade_tasks()
File "/opt/electrum/electrum/wallet_db.py", line 202, in _after_upgrade_tasks
self._load_transactions()
File "/opt/electrum/electrum/util.py", line 439, in <lambda>
return lambda *args, **kw_args: do_profile(args, kw_args)
File "/opt/electrum/electrum/util.py", line 435, in do_profile
o = func(*args, **kw_args)
File "/opt/electrum/electrum/wallet_db.py", line 1310, in _load_transactions
self.data = StoredDict(self.data, self, [])
File "/opt/electrum/electrum/json_db.py", line 79, in __init__
self.__setitem__(k, v)
File "/opt/electrum/electrum/json_db.py", line 44, in wrapper
return func(self, *args, **kwargs)
File "/opt/electrum/electrum/json_db.py", line 97, in __setitem__
v = self.db._convert_dict(self.path, key, v)
File "/opt/electrum/electrum/wallet_db.py", line 1361, in _convert_dict
v = dict((k, SwapData(**x)) for k, x in v.items())
```
Previously if there was a chain of exceptions, we were only
sending the traceback for the final exception.
E.g.
try:
raise ExcOne("asdasd")
except ExcOne() as e:
raise ExcTwo("qweqwe") from e
^ we would lose all info about ExcOne, including potentially many lines of trace
related #4905
related Electron-Cash/Electron-Cash@6a3d76b0ab
conceptually did not really make sense that the Exception_Hook kept a reference
to an ~arbitrary main window (preventing gc)
