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

spec/lib/url_helper_spec.rb

@@ -197,7 +197,7 @@ RSpec.describe UrlHelper do
 
       FileStore::S3Store.any_instance.stubs(:has_been_uploaded?).returns(true)
 
-      SiteSetting.secure_media = true
+      SiteSetting.secure_uploads = true
     end
 
     def cooked
@@ -209,12 +209,12 @@ RSpec.describe UrlHelper do
 
       it "returns the secure_proxy_without_cdn url, with no asset host URL change" do
         expect(cooked).to eq(
-          "//test.localhost/secure-media-uploads/dev/original/3X/2/e/2e6f2ef81b6910ea592cd6d21ee897cd51cf72e4.jpeg"
+          "//test.localhost/secure-uploads/dev/original/3X/2/e/2e6f2ef81b6910ea592cd6d21ee897cd51cf72e4.jpeg"
         )
       end
 
-      context "when secure_media setting is disabled" do
-        before { SiteSetting.secure_media = false }
+      context "when secure_uploads setting is disabled" do
+        before { SiteSetting.secure_uploads = false }
 
         it "returns the local_cdn_url" do
           expect(cooked).to eq(