feat(cli): support --template urls with file:// protocol

[icholy]

Related issue

Fixes #3656

Description

Update the --template flag to support file:// URIs for using local template files.

Example

cdktf init --template file://../my-template.zip

Checklist

• [x] I have updated the PR title to match CDKTF's style guide
• [x] I have run the linter on my code locally
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation if applicable
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works if applicable
• [x] New and existing unit tests pass locally with my changes

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[github-actions[bot]]

Hi there! 👋 We haven't heard from you in 60 days and would like to know if you're still working on this or need help. If we don't hear from you before then, I'll auto-close this PR in 30 days.

[icholy]

Still waiting for comment.

[icholy]

After some real-life experience with this, what I actually want to do is point it at a template directory. Having the template as a zip committed to the repo is pretty clunky. Also, the way I'm using the file:// scheme is not correct. file:// URIs do not support relative paths.

In light of this, I would like to change the design to work like this:

• If the template string is an exact match to a built-in template, use that.
• If the template string starts with http(s):// download the zip.
• Otherwise treat it like a local directory.

[github-actions[bot]]

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