Make some sort of table comparing all the methods and features we have for Infra/Agent

The following discussion from !69343 (merged) should be addressed:

• @marcia started a discussion: (+1 comment)

  @nagyv-gitlab review done, please take a look? 🏓

  Related:

  I think we should consider making some sort of table comparing all the methods and features we have for Infra. Something that says whether each feature or is deprecated or not, whether they're available in all tiers, etc.

  Smt like:

  Action	Method	Deprecated	Availability in tiers	Availablitluy in cluster levels
  Connect a cluster	Kubernetes Agent	No	Premium +	Project level
  Connect a cluster	Cluster certificates	Yes	All tiers	All levels

  If you agree, let's create a follow-up issue to discuss this. ;)