create generic init implementation

[dariuszd21]

What needs to get done

Generic InitCommand should be created, so all the crafts can use it, that allows:

• specifying name as an option and project_dir as a positional argument (the way cargo / uv works)
• use Jinja2 for templates
• support profiles e.g. by searching templates for subdirectories and listing them as options
• by default it will allow to be run in non-empty directory, as long as it creates only new files (no-overrides). This behavior may be overwritten (opt-out), so charmcraft will be able to error-out in non-empty directory

Why it needs to get done

Currently all the applications have a separate way of handling init.
We should create a generic version, that everyone can use.
It will enable create specific profiles in snapcraft, make our codebase smaller and it will be easier to maintain in the single place.

[syncronize-issues-to-jira]

Thank you for reporting us your feedback!

The internal ticket has been created: https://warthogs.atlassian.net/browse/CRAFT-3335.

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