[ios] Removes Zine implementation 2/N

Deletes the following legacy CS classes along with its usage:
content_suggestions_articles_header_item
content_suggestions_discover_item
content_suggestions_action_handler
content_suggestions_consumer

Deletes the following sections from the Model:
ContentSuggestionTypeArticle
ContentSuggestionTypeReadingList
ContentSuggestionTypeLearnMore

Bug: 1200303
Change-Id: I7bcb6ccb5981312b486845baae5c95f2b0a569d8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3170032
Reviewed-by: Adam Trudeau-Arcaro <adamta@google.com>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/main@{#923883}

ios/chrome/browser/ui/content_suggestions/BUILD.gn

@@ -4,12 +4,10 @@
 
 source_set("content_suggestions") {
   sources = [
-    "content_suggestions_action_handler.h",
     "content_suggestions_alert_factory.h",
     "content_suggestions_alert_factory.mm",
     "content_suggestions_category_wrapper.h",
     "content_suggestions_category_wrapper.mm",
-    "content_suggestions_consumer.h",
     "content_suggestions_coordinator.h",
     "content_suggestions_coordinator.mm",
     "content_suggestions_favicon_mediator.h",
@@ -116,13 +114,11 @@ source_set("constants") {
 
 source_set("content_suggestions_ui") {
   sources = [
-    "content_suggestions_action_handler.h",
     "content_suggestions_collection_controlling.h",
     "content_suggestions_collection_synchronizing.h",
     "content_suggestions_collection_updater.h",
     "content_suggestions_collection_updater.mm",
     "content_suggestions_commands.h",
-    "content_suggestions_consumer.h",
     "content_suggestions_data_sink.h",
     "content_suggestions_data_source.h",
     "content_suggestions_header_commands.h",

ios/chrome/browser/ui/content_suggestions/cells/BUILD.gn

@@ -31,12 +31,8 @@ source_set("cells") {
 
 source_set("cells_ui") {
   sources = [
-    "content_suggestions_articles_header_item.h",
-    "content_suggestions_articles_header_item.mm",
     "content_suggestions_discover_header_item.h",
     "content_suggestions_discover_header_item.mm",
-    "content_suggestions_discover_item.h",
-    "content_suggestions_discover_item.mm",
     "content_suggestions_header_item.h",
     "content_suggestions_header_item.mm",
     "content_suggestions_most_visited_action_cell.h",