FIX: Restructure temp/ folders for direct S3 uploads (#14137)

Previously we had temp/ in the middle of the S3 key path like so

* /uploads/default/temp/randomstring/test.png (normal site)
* /sitename/uploads/default/temp/randomstring/test.png (s3 folder path site)
* /standard10/uploads/sitename/temp/randomstring/test.png (multisite site)

However this necessitates making a lifecycle rule to clean up incomplete
S3 multipart uploads for every site, something which we cannot do. It makes
much more sense to have a structure with /temp at the start of the key,
which is what this commit does:

* /temp/uploads/default/randomstring/test.png (normal site)
* /temp/sitename/uploads/default/randomstring/test.png (s3 folder path site)
* /temp/standard10/uploads/sitename/randomstring/test.png (multisite site)

lib/file_store/base_store.rb

@@ -41,10 +41,11 @@ module FileStore
       File.join(path, "test_#{ENV['TEST_ENV_NUMBER'].presence || '0'}")
     end
 
-    def temporary_upload_path(file_name)
+    def temporary_upload_path(file_name, folder_prefix: "")
       File.join(
-        upload_path,
         TEMPORARY_UPLOAD_PREFIX,
+        folder_prefix,
+        upload_path,
         SecureRandom.hex,
         file_name
       )

lib/file_store/s3_store.rb

@@ -236,8 +236,7 @@ module FileStore
     end
 
     def temporary_upload_path(file_name)
-      path = super(file_name)
-      s3_bucket_folder_path.nil? ? path : File.join(s3_bucket_folder_path, path)
+      s3_bucket_folder_path.nil? ? super(file_name) : super(file_name, folder_prefix: s3_bucket_folder_path)
     end
 
     def object_from_path(path)