feat: add usage metrics

[iwilltry42]

Installation pulse and daily controller heartbeats with only version info, nothing else. Opt-Out via ACORN_USAGE_METRICS="disabled" or via install flag --disable-usage-metrics.

Development builds and non-official builds will be excluded by default (unless they explicitly add the target URL, etc.).

Also this PR updates the documentation to use the proxied images.acornlabs.com/acorn-io/runtime image instead of straight up ghcr.io/acorn-io/runtime, so we get more insights on image downloads.

To-Do

• [ ] Replace https://cdn.acrn.io/cli/mac_darwin_all/acorn et al with proxied URL (?)

Checklist

• [ ] The title of this PR would make a good line in Acorn's Release Note's Changelog
• [ ] The title of this PR ends with a link to the main issue being address in parentheses, like: This is a title (#1216). Here's an example
• [ ] All relevant issues are referenced in the PR description. NOTE: don't use GitHub keywords that auto-close issues
• [ ] Commits follow contributing guidance
• [ ] Automated tests added to cover the changes. If tests couldn't be added, an explanation is provided in the Verification and Testing section
• [ ] Changes to user-facing functionality, API, CLI, and upgrade impacts are clearly called out in PR description
• [ ] PR has at least two approvals before merging (or a reasonable exception, like it's just a docs change)