Geo: Part 2 of Enforce not null packages_package_files.file_store

What does this MR do?

Part 1: !38822 (merged)

This MR is the last part needed to enforce not null file_store on packages_package_files. This improves the performance of queries for locally stored package files since we no longer have to look for 1 and also NULL values.

Resolves #235516 (closed)

(Basically copy-paste-adjust-for-different-table of !42045 (merged))

Migration Output

Up:

== 20200915185707 EnsureFilledFileStoreOnPackageFiles: migrating ==============
== 20200915185707 EnsureFilledFileStoreOnPackageFiles: migrated (0.0372s) =====

== 20200915191156 ValidateNotNullFileStoreOnPackageFiles: migrating ===========
-- execute("ALTER TABLE packages_package_files VALIDATE CONSTRAINT check_4c5e6bb0b3;")
   -> 0.0004s
-- transaction_open?()
   -> 0.0000s
-- indexes(:packages_package_files)
   -> 0.0033s
-- remove_index(:packages_package_files, {:algorithm=>:concurrently, :name=>"index_packages_package_files_file_store_is_null"})
   -> 0.0035s
== 20200915191156 ValidateNotNullFileStoreOnPackageFiles: migrated (0.0090s) ==

Down:

== 20200915191156 ValidateNotNullFileStoreOnPackageFiles: reverting ===========
-- transaction_open?()
   -> 0.0000s
-- index_exists?(:packages_package_files, :id, {:where=>"file_store IS NULL", :name=>"index_packages_package_files_file_store_is_null", :algorithm=>:concurrently})
   -> 0.0032s
-- add_index(:packages_package_files, :id, {:where=>"file_store IS NULL", :name=>"index_packages_package_files_file_store_is_null", :algorithm=>:concurrently})
   -> 0.0079s
== 20200915191156 ValidateNotNullFileStoreOnPackageFiles: reverted (0.0114s) ==

== 20200915185707 EnsureFilledFileStoreOnPackageFiles: reverting ==============
== 20200915185707 EnsureFilledFileStoreOnPackageFiles: reverted (0.0000s) =====

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.