[Addon] Refactor: refactor chartmuseum addon with vela native components

[charlie0129]

Signed-off-by: Charlie Chiang charlie_c_0129@outlook.com

Description of your changes

• Use vela built-in components. No dependencies required, which means we no longer need fluxcd. So users can easily install this in air-gapped environments.
• Add image parameter to make air-gapped installation possible.
• Support specifying existing PVC (in addition to auto-generated) to persist data.
• Delete some inappropriate parameters due to the usage of built-in traits.

How has this code been tested?

Locally tested with some common parameters

Checklist

A tutorial on air-gapped installation of addons is planned.

I have:

• Title of the PR starts with type (e.g. [Addon] , [example] or [Doc]).
• Updated/Added any relevant documentation and examples.
• New addon should be put in experimental.
• Update addon should modify the version in metadata.yaml to generate a new version.
• Any changes about verified addons should be tested with CI script.