Launchpad: Handle invalid credentials files better

What needs to get done

If Launchpad.login errors out due to configparser issues, try deleting the credentials file and logging in again.
Why it needs to get done

This isn't an acceptable error message:
+ charmcraft remote-build --verbose --launchpad-accept-public-upload
Starting charmcraft, version 2.5.5.post102+g0f95a52
Logging execution to '/root/.local/state/charmcraft/log/charmcraft-20240226-125356.635385.log'
remote-build is experimental and is subject to change. Use with caution.
charmcraft internal error: No option 'consumer_key' in section: '1'
Full execution log: '/root/.local/state/charmcraft/log/charmcraft-20240226-125356.635385.log'
Traceback (most recent call last):
  File "/snap/charmcraft/x1/usr/lib/python3.10/configparser.py", line 791, in get
    value = d[option]
  File "/snap/charmcraft/x1/usr/lib/python3.10/collections/__init__.py", line 986, in __getitem__
    return self.__missing__(key)            # support subclasses that define __missing__
  File "/snap/charmcraft/x1/usr/lib/python3.10/collections/__init__.py", line 978, in __missing__
    raise KeyError(key)
KeyError: 'consumer_key'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/snap/charmcraft/x1/bin/charmcraft", line 8, in <module>
    sys.exit(main())
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/charmcraft/application/main.py", line 150, in main
    return app.run()
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/craft_application/application.py", line 465, in run
    return_code = dispatcher.run() or 0
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/craft_cli/dispatcher.py", line 487, in run
    return self._loaded_command.run(self._parsed_command_args)
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/craft_application/commands/base.py", line 171, in run
    result = self._run(parsed_args, **kwargs) or result
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/charmcraft/application/commands/remote.py", line 110, in _run
    builder = self._services.remote_build
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/craft_application/services/service_factory.py", line 95, in __getattr__
    instance.setup()
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/craft_application/services/remotebuild.py", line 69, in setup
    self.lp = self._get_lp_client()
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/craft_application/services/remotebuild.py", line 202, in _get_lp_client
    return launchpad.Launchpad.login(
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/craft_application/launchpad/launchpad.py", line 98, in login
    launchpadlib.launchpad.Launchpad.login_with(
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/launchpadlib/launchpad.py", line 700, in login_with
    return cls._authorize_token_and_login(
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/launchpadlib/launchpad.py", line 445, in _authorize_token_and_login
    cached_credentials = credential_store.load(
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/launchpadlib/credentials.py", line 345, in load
    return self.do_load(unique_key)
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/launchpadlib/credentials.py", line 486, in do_load
    return Credentials.load_from_path(self.filename)
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/lazr/restfulclient/authorize/oauth.py", line 229, in load_from_path
    credentials.load(credentials_file)
  File "/snap/charmcraft/x1/lib/python3.10/site-packages/lazr/restfulclient/authorize/oauth.py", line 205, in load
    consumer_key = parser.get(CREDENTIALS_FILE_VERSION, "consumer_key")
  File "/snap/charmcraft/x1/usr/lib/python3.10/configparser.py", line 794, in get
    raise NoOptionError(option, section)
configparser.NoOptionError: No option 'consumer_key' in section: '1'
-----
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2024-02-26 12:53:56 Restoring multipass:ubuntu-22.04-64:tests/spread/smoketests/remote-build:jammy (multipass:ubuntu-22.04-64)...
canonical / craft-application

Launchpad: Handle invalid credentials files better #241

What needs to get done

Why it needs to get done
