SKA: Relocate "platform" packages that remain on /packages (#208704)

## Summary

The `/packages` folder at the root of the Kibana repository used to
contain a lot of packages.
In the context of SKA, they have been gradually moved to various
locations:
* `src/platform/packages`
* `x-pack/platform/packages`
* `src/core/packages`

Currently, only `devOnly: true` packages are left in this folder. This
comprises libraries for CLI scripts as well as testing utilities.

With this PR, we are moving ~half of these packages under
`src/platform/packages/(private|shared)/`.
In particular, we are moving those packages that are being used from
platform and/or solutions.

Since they are `"devOnly": true`, this means they are ONLY used from
tests, cypress tests, storybook configs, ./scripts/ folders inside some
modules, or other non-prod-time logic. Nonetheless, they are effectively
referenced from platform and/or solutions code, hence I decided they
should be placed under `platform` folders.

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

dev_docs/tutorials/debugging_fips_test_failures.mdx

@@ -35,7 +35,7 @@ For an override related error the `expect(...)` will usually fail with typical e
 See the image below for an example of a test failure due to the license type being overridden:
 ![image][./fips_test_failure_license_override_example.png]
 
-The FIPS overrides can be found in the [fips_overrides.ts](https://github.com/elastic/kibana/blob/542a56b4829643d05c47bcc47485dd9baaacea32/packages/kbn-test/src/functional_tests/lib/fips_overrides.ts) file.
+The FIPS overrides can be found in the [fips_overrides.ts](https://github.com/elastic/kibana/blob/542a56b4829643d05c47bcc47485dd9baaacea32/src/platform/packages/shared/kbn-test/src/functional_tests/lib/fips_overrides.ts) file.
 
 For a FIPS/OpenSSL error, the error will be more cryptic/the test will fail to run, usually something like "digital envelope routines::unsupported". Generally these are related to Node.js's crypto module.
 

dev_docs/tutorials/performance/adding_performance_journey.mdx

@@ -16,7 +16,7 @@ Journey runs a flow of user interactions with Kibana in a browser and collects A
 It is possible to instrument Kibana with [custom performance metrics](https://docs.elastic.dev/kibana-dev-docs/tutorial/performance/adding_custom_performance_metrics),
 that will provide more detailed information about feature performance.
 
-Journeys core is [kbn-journeys](packages/kbn-journeys/README.mdx) package. It is a function test by design and is powered
+Journeys core is [kbn-journeys](src/platform/packages/private/kbn-journeys/README.mdx) package. It is a function test by design and is powered
 by [Playwright](https://playwright.dev/) end-to-end testing tool.
 
 ### Adding a new performance journey

dev_docs/tutorials/performance/running_performance_journey_in_cloud.mdx

@@ -20,7 +20,7 @@ The process takes a few steps:
 ### Re-configure deployment for Kibana and Elasticsearch
 We use [kibana-ops-e2e-perf](https://kibana-ops-e2e-perf.kb.us-central1.gcp.cloud.es.io/) cluster to monitor performance testing.
 
-If you would like to report APM metrics to this cluster, copy `SECRET_TOKEN` and `SERVER_URL` values from [packages/kbn-journeys/journey/journey_apm_config.ts](https://github.com/elastic/kibana/blob/60c82765779419d356a131e212682b69b035804b/packages/kbn-journeys/journey/journey_apm_config.ts#L10-L11)
+If you would like to report APM metrics to this cluster, copy `SECRET_TOKEN` and `SERVER_URL` values from [src/platform/packages/private/kbn-journeys/journey/journey_apm_config.ts](https://github.com/elastic/kibana/blob/60c82765779419d356a131e212682b69b035804b/src/platform/packages/private/kbn-journeys/journey/journey_apm_config.ts#L10-L11)
 
 #### Change Elasticsearch configuration
 In the ESS Admin Console, find your deployment and navigate to `Security` page. Click `Add Settings` under `Elasticsearch keystore` and add new entry: