PERF: Speed up `migrate_to_s3` rake task.

* Prioritizes non-image uploads
* Does one remap per upload instead of 3 remaps previously
* Every 100 uploads migrated, do 2 remaps which fixes broken
  URLs
* Exclude email_logs table from remap

lib/tasks/uploads.rake

@@ -232,12 +232,17 @@ def migrate_to_s3
     search_logs
     post_search_data
     notifications
+    email_logs
   }
 
   # Migrate all uploads
-  Upload.where.not(sha1: nil)
-    .where("url NOT LIKE '#{s3.absolute_base_url}%'")
-    .find_each do |upload|
+  file_uploads = Upload.where.not(sha1: nil).where("url NOT LIKE '#{s3.absolute_base_url}%'")
+  image_uploads = file_uploads.where("lower(extension) NOT IN (?)", FileHelper.supported_images.to_a)
+
+  [image_uploads, file_uploads].each do |uploads|
+    upload.find_in_batches(batch_size: 100) do |batch|
+      batch.each do |upload|
+        now = Process.clock_gettime(Process::CLOCK_MONOTONIC)
         # remove invalid uploads
         if upload.url.blank?
           upload.destroy!
@@ -249,7 +254,7 @@ def migrate_to_s3
         path = local.path_for(upload)
         # make sure the file exists locally
         if !path || !File.exists?(path)
-      putc "X"
+          puts "#{from} does not exist locally"
           next
         end
 
@@ -257,25 +262,30 @@ def migrate_to_s3
           file = File.open(path)
           content_type = `file --mime-type -b #{path}`.strip
           to = s3.store_upload(file, upload, content_type)
-    rescue
-      putc "X"
+        rescue => e
+          puts "Encountered an error while migrating #{upload.url}: #{e.class}: #{e.message}"
           next
         ensure
           file&.close
         end
 
         # remap the URL
-    [
-      [UrlHelper.absolute(from), Discourse.store.cdn_url(to)],
-      [UrlHelper.absolute_without_cdn(from), Discourse.store.cdn_url(to)],
-      [from, to],
-    ].each do |from_url, to_url|
-      DbHelper.remap(from_url, to_url, exclude_tables: exclude_tables)
+        DbHelper.remap(from, to, exclude_tables: exclude_tables)
+        upload.optimized_images.destroy_all
+        puts "Migrating #{from} --> #{to} took #{Process.clock_gettime(Process::CLOCK_MONOTONIC) - now} seconds"
       end
 
-    upload.optimized_images.destroy_all
-
-    putc "."
+      [
+        Discourse.asset_host,
+        Discourse.base_url_no_prefix
+      ].each do |from|
+        now = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+        from = "#{from}#{SiteSetting.Upload.s3_base_url}"
+        to = SiteSetting.s3_cdn_url
+        DbHelper.remap(from, to, exclude_tables: exclude_tables)
+        puts "Remapping #{from} --> #{to} took #{Process.clock_gettime(Process::CLOCK_MONOTONIC) - now} seconds"
+      end
+    end
   end
 end