Add graphql query to get project members count by role

What does this MR do and why?

Addresses #379059 (closed)

As a part of Support Role Based Approval Action for Scan Res... (&8018 - closed) we need to show the number of users in a project belonging to a role like in this design:

This change introduces a new graphql query projectMembersCountByRole within a project type that returns the count of users with their roles.

Graphql Query

query {
  project(fullPath:"flightjs/Flight") {
    projectMembersCountByRole {
      developer
      guest
      maintainer
      owner
      reporter
    }
  }
}

Response

{
  "data": {
    "project": {
      "projectMembersCountByRole": {
        "developer": 1,
        "guest": 1,
        "maintainer": 3,
        "owner": 2,
        "reporter": 1
      }
    }
  }
}

Database query

SELECT
    COUNT(*) AS count_all,
    "project_authorizations"."access_level" AS project_authorizations_access_level 
FROM
    "project_authorizations" 
WHERE
    "project_authorizations"."project_id" = 278964
GROUP BY
    "project_authorizations"."access_level"

Plan

  HashAggregate  (cost=2278.36..2278.41 rows=5 width=12) (actual time=5804.915..5804.918 rows=5 loops=1)
   Group Key: project_authorizations.access_level
   Buffers: shared hit=148 read=2207 dirtied=56
   I/O Timings: read=5724.579 write=0.000
   ->  Index Scan using index_unique_project_authorizations_on_project_id_user_id on public.project_authorizations  (cost=0.57..2270.83 rows=1505 width=4) (actual time=58.818..5792.339 rows=2358 loops=1)
         Index Cond: (project_authorizations.project_id = 278964)
         Buffers: shared hit=148 read=2207 dirtied=56
         I/O Timings: read=5724.579 write=0.000

console.postgres.ai

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