Removed switchToModelVersionAt from SO API definition (#219029)

## Summary
Part of https://github.com/elastic/kibana/issues/201807

**Strategy**:
This PR assumes that `switchToModelVersionAt` has done it’s job and all
SO type owners now use `modelVersions` instead of `migrations`.
It takes the approach of trusting that this is fine™

**Changes in this PR:**
- `switchToModelVersionAt` removed from all registered saved objects, so
their mapping hash had to be updated.
- Implements `globalSwitchToModelVersionAt` directly in `version_map`
- Updates logic to prioritize `modelVersions` over `migrations` in
`getLatestMappingsModelVersion`, that previously relied on
`switchToModelVersionAt` being set
- Updates unit tests to match the refactored logic
- Updates snapshots
- Adapts SO types registered in the **cases**, **SLO** and **encrypted
saved objects** plugins.
- Updates docs

**Risks**:
- Plugin developers disregard the deprecated status of `migrations` and
introduce new versions, which will not be BWC. Saved object type hash
changes will notify the core team for a code owner review. The core team
needs to investigate the related changes and provide feedback.


### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [x]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [x] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

---------

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

dev_docs/tutorials/saved_objects.mdx

@@ -19,7 +19,6 @@ import { SavedObjectsType } from 'src/core/server';
 export const dashboardVisualization: SavedObjectsType = {
   name: 'dashboard_visualization', [1]
   hidden: true, [3]
-  switchToModelVersionAt: '8.10.0', // this is the default, feel free to omit it unless you intend to switch to using model versions before 8.10.0
   namespaceType: 'multiple-isolated', [2]
   mappings: {
     dynamic: false,