Add Pipeline Schedules that supersedes experimental Trigger Schedule

app/assets/javascripts/gl_field_error.js

app/assets/javascripts/gl_field_errors.js

...s/pipeline_schedules/components/interval_pattern_input.js

...peline_schedules/components/pipeline_schedules_callout.js

...s/pipeline_schedules/components/target_branch_dropdown.js

...cripts/pipeline_schedules/components/timezone_dropdown.js

...vascripts/pipeline_schedules/icons/intro_illustration.svg

...ripts/pipeline_schedules/pipeline_schedule_form_bundle.js

...pts/pipeline_schedules/pipeline_schedules_index_bundle.js

app/assets/stylesheets/pages/pipeline_schedules.scss

app/controllers/projects/pipeline_schedules_controller.rb

app/finders/pipeline_schedules_finder.rb

app/helpers/gitlab_routing_helper.rb

app/helpers/pipeline_schedules_helper.rb

app/models/ci/pipeline.rb

app/models/ci/pipeline_schedule.rb

app/models/ci/trigger.rb

app/models/project.rb

app/policies/ci/pipeline_schedule_policy.rb

app/policies/project_policy.rb