Add pages_deployment model

Add a model to track pages deployments.

Can reuse some ideas from recently added https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/models/ci/pipeline_artifact.rb

Basically we can just copy

• ae485937
• 5df1c240

• reference project
• reference ci_build_job
• carrierwave field
• storage type(local/remote)