Add API for creating instance_amazon_s3_configuration for audit events

What does this MR do and why?

Add API for creating instance_amazon_s3_configurations for audit event streaming.

Screenshots or screen recordings

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Visit GraphiQL explorer https://gdk.test:3000/-/graphql-explorer
2. Run the following mutation to create a new AuditEvents::Instance::AmazonS3Configuration

mutation createInstanceAmazonS3Configuration {
  auditEventsInstanceAmazonS3ConfigurationCreate(input: {name: "AWS S3 Sanbox Instance", awsRegion: "us-east-1", accessKeyXid: "AKIA1234AKIA1234", secretAccessKey: "SECRET123SECRET123", bucketName: "gitlab-audit-logs"}) {
    errors,
    instanceAmazonS3Configuration{
      id,
      name,
      bucketName,
      accessKeyXid,
      awsRegion
    }
  }

3. You will get a response with the following format

{
  "data": {
    "auditEventsInstanceAmazonS3ConfigurationCreate": {
      "errors": [],
      "instanceAmazonS3Configuration": {
        "id": "gid://gitlab/AuditEvents::Instance::AmazonS3Configuration/9",
        "name": "AWS S3 Sanbox Instance",
        "bucketName": "gitlab-audit-logs",
        "accessKeyXid": "AKIA1234AKIA1234",
        "awsRegion": "us-east-1"
      }
    }
  }
}

4. Run the following in rails console and verify that a new record was created with correct attributes

AuditEvents::Instance::AmazonS3Configuration.last

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #423235 (closed)