Secrets storage with SecretKey encrypted (#22142)

Fork of #14483, but [gave up
MasterKey](https://github.com/go-gitea/gitea/pull/14483#issuecomment-1350728557),
and fixed some problems.

Close #12065.
Needed by #13539.

Featrues:
- Secrets for repo and org, not user yet.
- Use SecretKey to encrypte/encrypt secrets.
- Trim spaces of secret value.
- Add a new locale ini block, to make it easy to support secrets for
user.

Snapshots:

Repo level secrets:

![image](https://user-images.githubusercontent.com/9418365/207823319-b8a4903f-38ca-4af7-9d05-336a5af906f3.png)

Rrg level secrets

![image](https://user-images.githubusercontent.com/9418365/207823371-8bd02e93-1928-40d1-8c76-f48b255ace36.png)

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: KN4CK3R <admin@oldschoolhack.me>

models/migrations/migrations.go

@@ -442,6 +442,8 @@ var migrations = []Migration{
 	NewMigration("Add package cleanup rule table", v1_19.CreatePackageCleanupRuleTable),
 	// v235 -> v236
 	NewMigration("Add index for access_token", v1_19.AddIndexForAccessToken),
+	// v236 -> v237
+	NewMigration("Create secrets table", v1_19.CreateSecretsTable),
 }
 
 // GetCurrentDBVersion returns the current db version