Refactor and update mail templates (#35150)

- Moved mail templates to new directories.
- Added new devtest ymls.
- Embedded styles as much as possible.
- Added new translation keys for actions email.

---------

Signed-off-by: NorthRealm <155140859+NorthRealm@users.noreply.github.com>
Co-authored-by: delvh <dev.lh@web.de>

templates/mail/repo/actions/workflow_run.devtest.yml

@@ -0,0 +1,20 @@
+RunStatusText: Jobs status aggregation
+
+Repo:
+  FullName: Repo/Name
+
+Run:
+  WorkflowID: workflow.yml
+  HTMLURL: http://localhost/run/1
+
+Jobs:
+  - Name: Job-Name-1
+    Status: success
+    Attempt: 1
+    HTMLURL: http://localhost/job/1
+    Duration: 1h2m3s
+  - Name: Job-Name-2
+    Status: failure
+    Attempt: 2
+    HTMLURL: http://localhost/job/2
+    Duration: 1h2m3s