Allow multiple requirements for custom abilities

What does this MR do and why?

Previously, only one requirement was allowed to be specified for custom abilities. Now multiple requirements can be specified.

Issue: #432563 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Visit http://localhost:3000/-/graphql-explorer
2. Execute query:

   {
     memberRolePermissions {
       nodes {
         value
         requirements
       }
     }
   }

3. Verify the output includes:

   {
     "data": {
       "memberRolePermissions": {
         "nodes": [
           ...
           {
             "value": "ADMIN_VULNERABILITY",
             "requirements": [
               "READ_VULNERABILITY"
             ]
           },
           ...
         ]
       }
     }
   }