DEV: Add file_size_restriction site setting type (#24704)

This change will allow admins to configure file sizes in mb instead of
having to convert to kb.

Co-authored-by: Ella <ella.estigoy@gmail.com>

spec/lib/shrink_uploaded_image_spec.rb

@@ -86,7 +86,7 @@ RSpec.describe ShrinkUploadedImage do
     it "returns false when the upload is above the size limit" do
       post = Fabricate(:post, raw: "<img src='#{upload.url}'>")
       post.link_post_uploads
-      SiteSetting.max_image_size_kb = 0.001 # 1 byte
+      SiteSetting.max_image_size_kb = 0
 
       result =
         ShrinkUploadedImage.new(