EZP-31029: Introduced strict types for RoleService

[mikadamczyk]

Question	Answer
JIRA issue	EZP-31029
Bug/Improvement	yes
New feature	no
Target version	master
BC breaks	yes
Tests pass	yes
Doc needed	no

This PR introduces strict types for the \eZ\Publish\API\Repository\RoleService

Related to ezsystems/ezplatform-admin-ui#1111

TODO:

• Implement feature / fix a bug.
• Implement tests.
• Fix new code according to Coding Standards ($ composer fix-cs).
• Ask for Code Review.

QA

• Sanities for roles and policies management
• Sanities for assignment role to user/user group
• Sanities for unassignment role to user/user group
• Sanities for Roles tab in user's location view
• Sanities for Policies tab in user's location view
• Sanities for policies lists

[alongosz]

I skipped some redundant comments at the end, applies to almost every method in the Core layer.