Replace flake8 with ruff for linting

[remyroy]

What I did

Replaced flake8 with ruff for linting. We could eventually use ruff for formatting as well and I'll do some additional tests to see how this can be integrated better.

Related issue

Part of #179

[github-actions]

Test Coverage: Download HTML Report

Name                                                                 Stmts   Miss  Cover
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ethstaker_deposit/__init__.py                                            1      0   100%
ethstaker_deposit/bls_to_execution_change_keystore.py                   32      2    94%
ethstaker_deposit/cli/__init__.py                                        0      0   100%
ethstaker_deposit/cli/existing_mnemonic.py                              45      0   100%
ethstaker_deposit/cli/exit_transaction_keystore.py                      44      3    93%
ethstaker_deposit/cli/exit_transaction_mnemonic.py                      67      9    87%
ethstaker_deposit/cli/generate_bls_to_execution_change.py               62     11    82%
ethstaker_deposit/cli/generate_bls_to_execution_change_keystore.py      45      3    93%
ethstaker_deposit/cli/generate_keys.py                                  47      2    96%
ethstaker_deposit/cli/new_mnemonic.py                                   33      0   100%
ethstaker_deposit/cli/partial_deposit.py                                68      5    93%
ethstaker_deposit/cli/test_keystore.py                                  23      1    96%
ethstaker_deposit/credentials.py                                       206     76    63%
ethstaker_deposit/deposit.py                                            58     10    83%
ethstaker_deposit/exceptions.py                                          7      0   100%
ethstaker_deposit/key_handling/__init__.py                               0      0   100%
ethstaker_deposit/key_handling/key_derivation/__init__.py                0      0   100%
ethstaker_deposit/key_handling/key_derivation/mnemonic.py               95      6    94%
ethstaker_deposit/key_handling/key_derivation/path.py                   17      1    94%
ethstaker_deposit/key_handling/key_derivation/tree.py                   36      0   100%
ethstaker_deposit/key_handling/keystore.py                              98      0   100%
ethstaker_deposit/settings.py                                           31      0   100%
ethstaker_deposit/utils/__init__.py                                      0      0   100%
ethstaker_deposit/utils/ascii_art.py                                     2      0   100%
ethstaker_deposit/utils/click.py                                        84      3    96%
ethstaker_deposit/utils/config.py                                        3      0   100%
ethstaker_deposit/utils/constants.py                                    29      0   100%
ethstaker_deposit/utils/crypto.py                                       29      1    97%
ethstaker_deposit/utils/deposit.py                                       8      0   100%
ethstaker_deposit/utils/exit_transaction.py                             23      0   100%
ethstaker_deposit/utils/file_handling.py                                13      0   100%
ethstaker_deposit/utils/intl.py                                         55      3    95%
ethstaker_deposit/utils/ssz.py                                          60      7    88%
ethstaker_deposit/utils/terminal.py                                     29     21    28%
ethstaker_deposit/utils/validation.py                                  252     54    79%
----------------------------------------------------------------------------------------
TOTAL                                                                 1602    218    86%