[ResponseOps][Cases] Move hooks and APIs to a package

[cnasikas]

To empower solutions to build their UIs on top of Cases, we need to expose tools for making API calls in the case's backend. The cases plugin already has a rich set of API functions and react query hooks. We should move them to a package where solutions can import them.

DoD

• Create a package called @kbn/cases-apis.
• The package should be under the src/platform/packages/shared/response-ops folder.
• The folder should be named cases-apis.
• The type of the package should be shared-browser.
• The package contains have two folders: one called apis where all API functions will be and one called hooks where all React query hooks will be.
• A file called query_keys.ts will contain the react query keys and a file called mutation_keys.ts will contain the mutation keys.
• The package can import types and schemas from the cases plugin.

[elasticmachine]

Pinging @elastic/response-ops-cases (Feature:Cases)

[elasticmachine]

Pinging @elastic/response-ops (Team:ResponseOps)