[Feature] Add support for kibana space advanced settings

**Describe the resource you would like to have implemented.**
more user-friendly advanced settings for Kibana space

**Describe the solution you'd like**
new option with advanced_settings under elasticstack_kibana_space or new resource

**Describe alternatives you've considered**
I tried to use elasticstack_kibana_import_saved_objects. But there is a problem with upgrades. You have to manage a lot of fields like `typeMigrationVersion`, `coreMigrationVersion`, `buildNum`, ...

Currently, I created my provider which uses `/s/%s/internal/kibana/settings`

Review the implementation of elasticstack_kibana_space and the existing elasticstack_kibana_import_saved_objects flow, then inspect the /s/%s/internal/kibana/settings endpoint behavior. Define whether advanced_settings belongs on the space resource or a new resource, and verify upgrades do not require managing fields such as typeMigrationVersion, coreMigrationVersion, or buildNum.

Written by the indexing model from the issue text.