[meta] saved objects improvements

[pgayvallet]

Dedicated issue for the SO migration: #104083

Planned for 8.0

• PIT finder: add multi-namespace support - [saved objects][pit finder] Add support for multiple namespaces. #99044 (blocker for Saved objects import/export should include spaces #91615)
• Delete the legacy dashboard import/export API - Remove Dashboard Import/Export API #41439
• Upgrade import/export API to beta - Upgrade Saved Object import & export APIs to beta #90429
• Remove support for legacy export format Remove support for legacy imports from the UI #103921
  • Follow up task: Remove SO loader usages from SO management page - Decouple saved object management from SavedObjectLoader #67607
• Exclude specific objects during export - Ability to filter out items onExport or onImport #99680
• Remove v1 migration - [Core] Remove v1 migrations #96396
• Handling unknown SO types - Refuse to start with unknown saved object types in 8.0 #107678

Unprioritized atm

• Pre-migration state collection - Saved object migrations to allow pre-migration state collection #34996
• Include space information during import/export - Saved objects import/export should include spaces #91615
• Saved object type renaming - Support for cross-type Saved Object migration #91143
• Add bulk delete API - Delete saved objects in bulk #30503
• SO mig v2: dry run migration - Dry run migrations #55404
• Read-only saved objects - [Saved Objects] Prevent users from altering managed assets #70461
• Move saved objects between indices - Migrate saved-object types between indices #90817
• Eventually consistent / deferred migration - Eventually consistent saved object/data index migrations #96626
• Support pretty format in import/export - Support for pretty format in Saved Object import and export #103021

[elasticmachine]

Pinging @elastic/kibana-core (Team:Core)