refactor cluster create command (frontend only)

[Orzelius]

closes #10289
related: #10133, #10287

Changes

User facing

• Add two sub-commands cluster create qemu and cluster create docker
  • The commands only have flags relevant to the applicable providers (cluster create still functions all the same)
• Error if invalid provider's flags are passed (both new and old cluster create commands) (previously not all the flags were checked). This is technically a breaking change. Please let me know if it should be a warning at first.
• Add (QEMU only) or (docker only) at the start of the flag description
• In command description (e.g. cluster create -h) group flags by providers and then sort alphabetically.

See results to the command documentation in the reference docs

Internal

• Split common code into the clustermaker package
• Split qemu and docker code
• Add basic unit tests for all options
• Split common and provider specific cli options into separate structs and flag groups.

other

• Use default kubeconfig instead of the previous kubeconfig.SinglePath()which errors if multiple configs are defined

Notes to reviewers

This might look like a massive change, but it's mostly just moving existing logic around with added tests. I've failed to get the integration tests running locally, so I'd love to see the results of a ci run and will fix any issues if they come up. As I can't perform thorough qemu testing on my mac machine I'm fairly certain some bugs remain, but they should be easy to fix once found thanks to the testable logic and clear separation of concerns.

Please let me know if I've missed something or if you have any ideas <3

[Orzelius]

Test that there are tests for all the common fields.

Please let me know if this is inappropriate or if there's a less hacky way to achieve the same result or if I should just change it to good ol' fashioned tests

[Orzelius]

Update: rebased latest changes from main and removed the KVM change to reduce the scope of the pr.

[Orzelius]

If this is too big of a change to confidentially merge all at once please let me know. It would take some extra work, but I could split it into smaller, easier to review pieces. For example as follows:

1. Split flags and options into separate provider specific structs
2. Dependency inject provider and add tests
3. Split out common logic
4. Split qemu and docker logic
5. Add separate create docker and create qemu commands

This would result in a easier to review diffs where possible mistakes are easier to spot.

If you generally disagree with the approach or implementation on broader terms please describe a more suitable solution in the #10289 issue.