Add Scanner ID filter to vulnerabilitySeveritiesCount

What does this MR do?

This MR adds Scanner ID filter to vulnerabilitySeveritiesCount GraphQL query.

Screenshots (strongly suggested)

{
  project(fullPath: "root/security-reports-new") {
    vulnerabilitySeveritiesCount(scannerId: "gid://gitlab/Vulnerabilities::Scanner/187") {
      critical
      high
      medium
      low
      info
      unknown
    }
  }
}

{
  "data": {
    "project": {
      "vulnerabilitySeveritiesCount": {
        "critical": 2,
        "high": 8,
        "medium": 0,
        "low": 0,
        "info": 0,
        "unknown": 0
      }
    }
  }
}

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.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Related to #332139 (closed)