Delete all CommitStatus for project_id

Move the for_project(ids) scope from Ci::Build to CommitStatus so it
can be reused across both classes.

app/models/ci/build.rb

@@ -190,8 +190,6 @@ module Ci
     scope :without_coverage, -> { where(coverage: nil) }
     scope :with_coverage_regex, -> { where.not(coverage_regex: nil) }
 
-    scope :for_project, -> (project_id) { where(project_id: project_id) }
-
     acts_as_taggable
 
     add_authentication_token_field :token, encrypted: :required

app/models/commit_status.rb

@@ -53,6 +53,7 @@ class CommitStatus < Ci::ApplicationRecord
   scope :before_stage, -> (index) { where('stage_idx < ?', index) }
   scope :for_stage, -> (index) { where(stage_idx: index) }
   scope :after_stage, -> (index) { where('stage_idx > ?', index) }
+  scope :for_project, -> (project_id) { where(project_id: project_id) }
   scope :for_ref, -> (ref) { where(ref: ref) }
   scope :by_name, -> (name) { where(name: name) }
   scope :in_pipelines, ->(pipelines) { where(pipeline: pipelines) }
@@ -68,7 +69,8 @@ class CommitStatus < Ci::ApplicationRecord
     # Pluck is used to split this query. Splitting the query is required for database decomposition for `ci_*` tables.
     # https://docs.gitlab.com/ee/development/database/transaction_guidelines.html#database-decomposition-and-sharding
     project_ids = Project.where_full_path_in(Array(paths)).pluck(:id)
-    where(project: project_ids)
+
+    for_project(project_ids)
   end
 
   scope :with_preloads, -> do

app/services/projects/destroy_service.rb

@@ -150,7 +150,7 @@ module Projects
         ::Ci::DestroyPipelineService.new(project, current_user).execute(pipeline)
       end
 
-      deleted_count = project.commit_statuses.delete_all
+      deleted_count = ::CommitStatus.for_project(project).delete_all
 
       Gitlab::AppLogger.info(
         class: 'Projects::DestroyService',