Add container based executors to UI

[fivenp]

Describe the enhancement you'd like to see As we added container based functionalities to our CRDs (#2293) we nede to replicate this behaviour on the UI.

Additional context As a user I'd like to be able to create multiple container based executors through the UI and add tests relying on them.

This feature will trigger a bigger restructure of our current executors view.

1. We will have to split the view into custom executors and official executors (which is the current view we already have)
2. We will need to make sure to implement the creation flow and the executor settings
3. The mocks also contain some more analytical data on custom executors (e.g. tests using this executor, executions, etc) – we can ignore these analytical details in this iteration :)

Figma

https://www.figma.com/file/asfUPepLHtyutWWR0pNGfK/Testkube-V2?node-id=1576%3A60765