FIX: Streamline topic bump functionality and notification settings behaviour (#34945)

Followup 2a65bf4522

With the above change, we inadvertently made it so that
when you edited the topic title or category, we bumped
the topic.

This fix makes it so we do not bump topics when only title, category,
or tags are changed, to restore the previous behaviour.

In addition, we are making it so the following settings no longer
influence topic bump behaviour, keeping only their intended notification
behaviour around. The site setting description never mentioned anything
about topic bumps:

* disable_category_edit_notifications
* disable_tag_edit_notifications

lib/post_revisor.rb

@@ -587,7 +587,7 @@ class PostRevisor
   end
 
   def create_revision
-    modifications = post_changes.merge(@topic_changes.diff)
+    modifications = post_changes.merge(topic_diff)
 
     modifications["raw"][0] = cached_original_raw || modifications["raw"][0] if modifications["raw"]
 
@@ -608,7 +608,7 @@ class PostRevisor
   def update_revision
     return unless revision = PostRevision.find_by(post_id: @post.id, number: @post.version)
     revision.user_id = @post.last_editor_id
-    modifications = post_changes.merge(@topic_changes.diff)
+    modifications = post_changes.merge(topic_diff)
 
     modifications.each_key do |field|
       if revision.modifications.has_key?(field)
@@ -641,7 +641,7 @@ class PostRevisor
   end
 
   def topic_diff
-    @topic_changes.diff
+    @topic_changes.diff.with_indifferent_access
   end
 
   def perform_edit
@@ -662,14 +662,19 @@ class PostRevisor
   end
 
   def bypass_bump?
-    !@post_successfully_saved || post_changes.any? || @topic_changes.errored? ||
-      @opts[:bypass_bump] == true || @post.whisper? || only_hidden_tags_changed?
+    return true if @opts[:bypass_bump] == true
+    return true if @post.whisper? || !@post_successfully_saved || post_changes.any?
+    return true if @topic_changes.errored?
+    return true if topic_title_changed? || topic_category_changed? || topic_tags_changed?
+    return true if only_hidden_tags_changed?
+
+    false
   end
 
   def only_hidden_tags_changed?
     return false if (hidden_tag_names = DiscourseTagging.hidden_tag_names).blank?
 
-    modifications = post_changes.merge(@topic_changes.diff)
+    modifications = post_changes.merge(topic_diff)
     if modifications.keys.size == 1 && (tags_diff = modifications["tags"]).present?
       a, b = tags_diff[0] || [], tags_diff[1] || []
       changed_tags = ((a + b) - (a & b)).map(&:presence).compact
@@ -732,7 +737,7 @@ class PostRevisor
 
   def publish_changes
     options =
-      if !@topic_changes.diff.empty? && !@topic_changes.errored?
+      if !topic_diff.empty? && !@topic_changes.errored?
         { reload_topic: true }
       else
         {}
@@ -764,6 +769,16 @@ class PostRevisor
       !@topic_changes.errored?
   end
 
+  def topic_category_changed?
+    topic_changed? && @fields.has_key?(:category_id) && topic_diff.has_key?(:category_id) &&
+      !@topic_changes.errored?
+  end
+
+  def topic_tags_changed?
+    topic_changed? && @fields.has_key?(:tags) && topic_diff.has_key?(:tags) &&
+      !@topic_changes.errored?
+  end
+
   def reviewable_content_changed?
     raw_changed? || topic_title_changed?
   end