[SPIKE] Make Epiphany upgrades selective (Kafka)

Description

In this spike we want to consider an option with selective Kafka upgrades by Epicli.

It should be relatively simple (likely requires no changes in upgrade procedures themselves) to refactor Epiphany upgrades and make it possible for the user to control what components will be upgraded. That may bring value not only to users with legacy clusters but also to the process of testing.

• It needs to be checked if Kafka supports upgrades from any version to any other version. If it requires incremental upgrades between versions, it have to be taken into account.
• The output of this task is a PoC with selective Kafka upgrade by epicli.
• If it’s possible, design document can be created.

All the topics related to the Kafka module will be done separately and covered by #1976 task and tasks that will be created as a result of #1976.

Additional information

The original task contained additional options related to Kafka module, but to avoid dependencies and clarify a single topic per task, these options are not covered here:

2. In the near future we will start introducing modules that will replace classic Epiphany components (like Kafka clusters etc). If we'd do that soon enough then the question would be if there is a possiblity to reuse modules with exising legacy on-prem clusters and what needs to be done to achieve that.

3. Support both 1. and 2.

We'd like to understand how much work do these options require to be implemented.

We want a design-doc out of his research. 

[przemyslavic]

@ar3ndt We urgently need these fixes:

1. The when conditions are invalid. Regardless of what components we select for the upgrade, all of them will be upgraded, because the conditions are always resolved as true.

Instead of the condition when: ('"kafka" in upgrade_components') or upgrade_components|length == 0 the condition when: "'kafka' in upgrade_components or upgrade_components|length == 0" seems to work fine. The first condition always returns true (thanks @to-bar for debugging this together).

1. It looks like the condition is missing here at all which runs the kubernetes role even though I only set the kafka to be updated.
2. It would be nice to have the values sorted alphabetically here and separated additionally by a space for readability.

Moving this task back to TODO.

[przemyslavic]

1, 2, 3 Fixed. User can run the upgrade command with an optional argument --upgrade-components providing the list of components to be updated. Running the command without this argument will update all components.