Fix help text for `exaslct`

[tomuben]

The help text (when running exaslct --help) shows:

Usage: exaslct [OPTIONS] COMMAND [ARGS]...

  ITDE - Integration Test Docker Environment

  Create and control a docker based exasol database test setup.

  Examples:

      Check the health of the execution environment:

          $ itde health

      Spawn an ITDE test environment:

          $ itde spawn-test-environment --environment-name test \
          --database-port-forward 8563 --bucketfs-port-forward 2580 \
          --docker-db-image-version 7.1.9 --db-mem-size 4GB

Options:
  --help  Show this message and exit.

Commands:
  build                         Builds a script-languages-container.
...

=> The commands are correct, but the heading is used from itde.
The reason is that we use the same cli() routine from itde, see:

script-languages-container-tool/exasol/slc/tool/main.py

Line 4 in be9f853

from exasol_integration_test_docker_environment.cli.cli import cli # type: ignore

We need to implement a separate routine with it's own help text.