DEV: Rename secure_media to secure_uploads (#18376)

This commit renames all secure_media related settings to secure_uploads_* along with the associated functionality.

This is being done because "media" does not really cover it, we aren't just doing this for images and videos etc. but for all uploads in the site.

Additionally, in future we want to secure more types of uploads, and enable a kind of "mixed mode" where some uploads are secure and some are not, so keeping media in the name is just confusing.

This also keeps compatibility with the `secure-media-uploads` path, and changes new
secure URLs to be `secure-uploads`.

Deprecated settings:

* secure_media -> secure_uploads
* secure_media_allow_embed_images_in_emails -> secure_uploads_allow_embed_images_in_emails
* secure_media_max_email_embed_image_size_kb -> secure_uploads_max_email_embed_image_size_kb

app/models/upload.rb

@@ -186,7 +186,7 @@ class Upload < ActiveRecord::Base
     "upload://#{short_url_basename}"
   end
 
-  def uploaded_before_secure_media_enabled?
+  def uploaded_before_secure_uploads_enabled?
     original_sha1.blank?
   end
 
@@ -204,14 +204,14 @@ class Upload < ActiveRecord::Base
   end
 
   def self.consider_for_reuse(upload, post)
-    return upload if !SiteSetting.secure_media? || upload.blank? || post.blank?
-    return nil if !upload.matching_access_control_post?(post) || upload.uploaded_before_secure_media_enabled?
+    return upload if !SiteSetting.secure_uploads? || upload.blank? || post.blank?
+    return nil if !upload.matching_access_control_post?(post) || upload.uploaded_before_secure_uploads_enabled?
     upload
   end
 
-  def self.secure_media_url?(url)
+  def self.secure_uploads_url?(url)
     # we do not want to exclude topic links that for whatever reason
-    # have secure-media-uploads in the URL e.g. /t/secure-media-uploads-are-cool/223452
+    # have secure-uploads in the URL e.g. /t/secure-uploads-are-cool/223452
     route = UrlHelper.rails_route_from_url(url)
     return false if route.blank?
     route[:action] == "show_secure" && route[:controller] == "uploads" && FileHelper.is_supported_media?(url)
@@ -219,14 +219,14 @@ class Upload < ActiveRecord::Base
     false
   end
 
-  def self.signed_url_from_secure_media_url(url)
+  def self.signed_url_from_secure_uploads_url(url)
     route = UrlHelper.rails_route_from_url(url)
     url = Rails.application.routes.url_for(route.merge(only_path: true))
     secure_upload_s3_path = url[url.index(route[:path])..-1]
     Discourse.store.signed_url_for_path(secure_upload_s3_path)
   end
 
-  def self.secure_media_url_from_upload_url(url)
+  def self.secure_uploads_url_from_upload_url(url)
     return url if !url.include?(SiteSetting.Upload.absolute_base_url)
     uri = URI.parse(url)
     Rails.application.routes.url_for(