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>

services/mailer/mail_release.go

@@ -19,7 +19,7 @@ import (
 	sender_service "code.gitea.io/gitea/services/mailer/sender"
 )
 
-const tplNewReleaseMail templates.TplName = "release"
+const tplNewReleaseMail templates.TplName = "repo/release"
 
 func generateMessageIDForRelease(release *repo_model.Release) string {
 	return fmt.Sprintf("<%s/releases/%d@%s>", release.Repo.FullName(), release.ID, setting.Domain)