Cardano Updates

Fix governance tests when running on long running testnets

Raise a ValueError when attempting to get default governance on testnets.
This ensures that the function does not proceed with unsupported operations
on testnet environments.

Making sure the test can run without setting up governance first.

The @pytest.mark.testnets decorator was removed from the
test_guardrails method in the TestGovernanceGuardrails class.

The guardrails tests cannot currently run on testnets. We need to modify
the tests to not try to update the guardrails script on testnets.

refactor(tests): update old pre-Conway poll tests

Make the poll tests work in Conway.

- Update docstrings to reflect pre-Conway governance functionality
- Remove version checks for Babbage transaction era
- Replace direct transaction build and submit calls with utility function
- Adjust error assertions to include new possible error messages

The old poll functionality doesn't work in Conway.

Add ability to search for expected messages in log files

Add expected log message check for protocol version in `TestHardfork`.

This ensures that the correct protocol version is logged during the
hardfork enactment process.

Refactored the `expect_errors` function by extracting the log message
checking logic into a separate `_check_msgs_presence_in_logs` function.
Added a new `expect_messages` context manager for checking expected
messages in logs. This improves code readability and reusability.

refactor(tests): remove unneeded fixtures in test files

Removed unneeded fixtures `skip_leadership_schedule` and `skip_hf_command`
from `test_blocks.py` and `test_hardfork.py` respectively. These fixtures
were checking for the availability of certain CLI commands, which are
available in all recent node versions.

This change simplifies the test code and removes unnecessary checks.

feat(protocol): update protocol param keys for Conway

- Removed unused imports and constants related to protocol param keys
- Updated `PROTOCOL_PARAM_KEYS` to include new parameters for Conway
- Removed conditional logic for protocol param keys based on versions

chore(ci): remove xtrace from node upgrade script

chore(deps): bump dawidd6/action-send-mail from 3 to 4

Removed the 'set -x' option from the node_upgrade_pytest.sh script to
disable xtrace and reduce verbosity in CI output.

Bumps [dawidd6/action-send-mail](https://github.com/dawidd6/action-send-mail) from 3 to 4.
- [Release notes](https://github.com/dawidd6/action-send-mail/releases)
- [Commits](https://github.com/dawidd6/action-send-mail/compare/v3...v4)

---
updated-dependencies:
- dependency-name: dawidd6/action-send-mail
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

chore: update venv directory path

Updated the virtual environment directory path from .env to .venv in the
setup_venv.sh script to follow standard naming conventions.

chore(nix): remove python devshell from flake.nix

Updated comments in flake.nix to clarify the use of the IOG nix cache.
Simplified the comment to make it more concise and clear.

The python devshell has been removed from flake.nix as the sync tests
are being fully moved to a separate repository. This change cleans up
the flake configuration by removing the unnecessary python shell.

feat: refactor flake.nix to use nodePkgs variable

Refactored flake.nix to introduce nodePkgs variable for cardano-node
packages. This change improves readability and maintainability by
replacing repeated cardano-node package references with nodePkgs.