Context refactoring. Move Issues list, Search logic to context

app/contexts/commit_load_context.rb

app/contexts/issues_list_context.rb

app/contexts/merge_requests_load_context.rb

app/contexts/search_context.rb

app/controllers/commit_controller.rb

app/controllers/dashboard_controller.rb

app/controllers/groups_controller.rb

app/controllers/issues_controller.rb

app/controllers/merge_requests_controller.rb

app/controllers/milestones_controller.rb

app/controllers/refs_controller.rb

app/controllers/search_controller.rb

app/helpers/issues_helper.rb

app/models/event.rb

app/roles/issue_commonality.rb