Update project dependencies and metadata

[stankudrow]

This PR improves the project in many ways even not touching the core logic:

• Project dependencies and metadata:

  • Moving to the python 3.9 as the minimum supported version. The end-of-life for Python 3.8 is 31 Oct 2024, so the transition can be made in advance. By this step the project drops the Python3.7 support (EOL is 27 Jun 2023).
  • The pytest package and its plugins as project dependencies moved into the separate test section. Its configuration got enhanced by: 1) capturing stream outputs (-s) with 2) increased verbosity (-vvv); the session stops if 3) any test fails (--maxfail=1); also 4) the tests can be launched in a random order, which is good for preventing the cases of determinism.
  • The CHANGELOG.md file was updated with the v0.2.4 contributions records.

• Code and test bases:

  • added the DEFAULT_HOST="127.0.0.1" constant;
  • more type hints;
  • the custom event_loop was removed from the conftest.py file -> no more deprecation warning on this matter;
  • some tests were changed to make them pass having launched the ClickHouse container with docker run --rm -p 9000:9000 --name some-clickhouse-server clickhouse/clickhouse-server.

@long2ice , let's review all of this, especially tests, I need this PR to be cross-validated. Who else can I tag to help me with review? any maintainers or volunteers?

[stankudrow]

@long2ice , shall we work out this PR?

Also, I think that a future PR introducing the mypy package would be nice. I'll see how many changes it may result in.

[long2ice]

Thanks!