Draft: Migrate to UrfaveCLI v3

[acheong08]

Proposed Changes

Migrate to urfaveCLI v3, following the migration guide. Notable changes include:

• StringSliceFlag -> []string
• EnvVars: []string{} -> cli.EnvVars()
• MAJOR CHANGE: cli.Context has been completely removed

Types of Changes

CLI migration

Verification

¯_(ツ)_/¯ - TODO - Works on my machine

Testing

Linked Issues

• k3s fish completion #6612

User-Facing Change

`-i` option for `k3s completion` removed to allow for auto generated completions. TBD - Might be rolled back and simply add hard coded fish/powershell completions following previous style

Further Comments

I did this purely to have fish autocomple. Feel free to ignore.

[acheong08]

There are still issues to be resolved, namely

• fix: make fish completions work urfave/cli#2096

Fish completion still doesn't work properly

[dereknola]

Due to how containerd is embedded inside K3s, we cannot move to urfaveCLI v3 until that project also moves to it. I handled the migration to V2... and it took 2 years to complete that project.

[acheong08]

Due to how containerd is embedded inside K3s

Yup I noticed there were still places that relied on v2 - rip. I might just use the partial migration to generate fish completions and that's it