GraphQL endpoint for exposing agent configuration details for a project

What does this MR do?

• Introduces a mechanism for the GitLab backend to communicate with KAS:
  • Communication is via gRPC, with interfaces provided by the kas-grpc gem.
  • Authentication uses a JWT, with the pre-existing .gitlab_kas_secret as the secret.
• Adds a GraphQL type and resolver to return the names of any agents a project has configured (via config files in .gitlab/agents/)

GraphQL examples

request:

{
  project(fullPath: "example-group/project-with-agent-config") {
    name
    
    agentConfigurations {
      nodes {
        agentName
      }
    }
  }
}

response:

{
  "data": {
    "project": {
      "name": "project-with-agent-config",
      "agentConfigurations": {
        "nodes": [
          {
            "agentName": "example-agent"
          },
          {
            "agentName": "example-second-agent"
          }
        ]
      }
    }
  }
}

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• [-] I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

#327853 (closed)