Improve TableSizeService

Ref: gitlab-org/gitlab#506841 (closed)

What does this MR do?

This MR adds all the necessary information to ping the relevant team when creating an issue automatically.

• Attach all issues to epic_id
• Add the associated labels based on the feature category

Testing

• Create a PAT token and run the following script in notifier

require_relative 'gitlab_api_client'
require_relative 'table_size_service'


TableSizeService.new(
  GitlabApiClient.new('https://gitlab.com/api/v4').call,
  '62927330',
  'spec/fixtures',
  1
).execute