Draft some new admonitions

[lcawl]

This PR adds some admonitions for serverless- and ESS-specific admonitions:

• beta_ess
• beta_serverless
• dev_ess
• dev_serverless
• ga_serverless
• ga_stack
• ga_ess
• deprecated_ess
• deprecated_serverless
• discontinued_ess
• discontinued_serverless
• discontinued_stack
• coming_ess
• coming_serverless

The work similar to the existing admonitions, for example:

NOTE: The rubocop config file change works around the following make error:

lib/care_admonition/extension.rb:100:3: C: Metrics/MethodLength: Method has too many lines. [31/20]

TBD: Are there other combinations that we'll need (e.g. "ga_all" to have a single admonition that covers all contexts)?

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[leemthompo]

• I'd like a simple "Not available on serverless" tag too :)
• I guess we should s/Elastic Serverless/Elastic Cloud Serverless/g

[leemthompo]

@lcawl if you approve I can push a commit for my suggestions

[colleenmcginnis]

What is the difference between deprecated and discontinued? Can we make the discontinued description more specific?

[lcawl]

We haven't had "discontinued" before but it arose in discussions like elastic/kibana#192292. Currently we just remove content when the pertinent feature goes from "deprecated" to discontinued/removed/no longer available. If our pages span multiple versions, however, or if we want to give folks a clear indication of when a feature will be removed, it seems like this might be something we'll want to have a way of calling out.