Scaffold an execution-environment project using init subcommand

[shatakshiiii]

SUMMARY

This PR adds support to scaffold an execution-execution project that can build an EE image that can be pushed and published to ghcr.

Github action workflow scaffolded through this EE project is calling a re-usable workflow from ansible-content-actions repo: https://github.com/ansible/ansible-content-actions/blob/main/.github/workflows/ee-build.yml

CLI Changes:

Adds execution_env as a project type in init subcommand.

ansible-creator init execution_env /path/to/sample_ee_project

Testing and Documentation:

• Unit and integration tests have been added in this PR itself.
• Additionally ansible-navigator commands are executed in the workflow to test if its a viable execution-environment.
• The upstream RTD documentation is being updated for these changes in a separate PR that refactors our developer docs: Refactor developer docs #370

A sample personal project that uses this re-usable workflow to build and push an EE: https://github.com/shatakshiiii/ee_project

Related JIRA: AAP-40560 and AAP-38339