Add init package downloader

[jeff-mccoy]

Description

Enhanced the quick start process for testing Zarf by prompting users to download the init package if it can't be found locally.

Related Issue

Closes #502

Type of change

• New feature (non-breaking change which adds functionality)

[jeff-mccoy]

So there's an interesting issue with some envs (like use a debug, go run and CI), the version is either "unset" or "UnknownVersion". It probably wasn't necessary but I went ahead and added the ability on invalid cli version to get the latest release's init tarball. Bonus this will later make it trivial to check for the latest version of Zarf if online.

Standard download message with "yes" chosen:

Error message with "no" chosen:

Automatica release lookup from github:

[jeff-mccoy]

actually with our lack of interactive cli testing, I don't think there's a good way to test this in CI right now, now that I think about it. If we do --confirm, needed to confirm the download it would also start to init the wrong version of zarf in a cluster, which wouldn't be great. Not to mention forcing hundreds of megs in extra downloads per pipeline run. Hmmm.....

[YrrepNoj]

Thanks for updating the PR. This update will be a nice QoL change and reduce friction to getting started with Zarf.