Policy Store API: Convert /policies/paged into POST

[dsmf]

As Policy Store API user,
I want that the GET /policies/paged endpoint is converted to POST,
so that the URL cannot get too long anymore if many search criteria and sort parameters are applied.

Hints / Details

• relates to [POLICY_STORE] Add filter, sorting, pagination for GET endpoints #639
• relates to [POLICY_STORE] Multi-Filter support for API endpoint GET /irs/policies #750
• (?) Should we convert the endpoint or implement a new one for POST?

Acceptance Criteria

• GET /policies/paged endpoint is converted to POST endpoint

Out of Scope

• ...