[Stateful sidenav] Add cloud yml setting for onboarding default solution

[sebelga]

In this PR I've exposed a new yml setting from the cloud plugin to forward the use case (solution) selected by the user during deployment onboarding creation.

The use case in Cloud is not typed and any string can be provided. From what @AlexP-Elastic found out, the current values passed are: "elasticsearch", "observability", "security", "Security" (uppercase).

I handled the case and ignored any string that does not match one of the known values.
For consistency I mapped the value to the Kibana naming: "es", "oblt" and "security".

New yml setting

# Allowed values: elasticsearch | observability | security
xpack.cloud.onboarding.default_solution: elasticsearch

Update cloud API

The defaultSolution value is exposed by the cloud plugin setup contract (both server and public) under onboarding.

{
  ...,
  onboarding: {
    defaultSolution: 'es', // es, oblt, security
  }
}

This value will have to be read by the security team when creating the default space on new deployment. cc @legrego

[sebelga]

/ci

[sebelga]

/ci

[sebelga]

/ci

[elasticmachine]

Pinging @elastic/appex-sharedux (Team:SharedUX)

[azasypkin]

Changes in test/plugin_functional/test_suites/core_plugins/rendering.ts LGTM.

[kpollich]

Fleet codeowners

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: ba86097
• Storybooks Preview

Failed CI Steps

• FTR Configs #91

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
cloud	11	12	+1

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
cloud	17	19	+2

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
cloud	6.3KB	6.6KB	+371.0B

Unknown metric groups

API count

id	before	after	diff
cloud	74	78	+4

History

• 💔 Build #214481 failed 1a85cb5
• 💔 Build #214454 failed 6f83f64
• 💔 Build #214415 failed e8001d55a19a3f551beb51890ec998c2f09ce71a
• 💔 Build #214099 failed fb961b83764b3cfbb47104182de7513a778c8d6d

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @sebelga