feat(ui): show effective user permissions on Users page

[sranka]

This PR ensures that effective user permissions (including permissions from user roles) are shown on the Users Page.

The example above demonstrates effective permissions in action:

• test1 role grants Write on [_internal,a,b] databases, user lojza has only this role and no extra granted permissions
• test2 role grants Read on [a,b] databases, user pavel has only this role and no extra granted permissions
• effective permissions for user pepa are shown, they represent user granted permissions (Write on x3 database) and all permissions granted by assigned roles (test1, test2)

It is a part of the solution to #5834

• CHANGELOG.md updated with a link to the PR (not the Issue)
• Well-formatted commit messages
• Rebased/mergeable
• Tests pass