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>

options/locale/locale_en-US.ini

@@ -3212,3 +3212,19 @@ owner.settings.cleanuprules.remove.days = Remove versions older than
 owner.settings.cleanuprules.remove.pattern = Remove versions matching
 owner.settings.cleanuprules.success.update = Cleanup rule has been updated.
 owner.settings.cleanuprules.success.delete = Cleanup rule has been deleted.
+
+[secrets]
+secrets = Secrets
+description = Secrets will be passed to certain actions and cannot be read otherwise.
+none = There are no secrets yet.
+value = Value
+name = Name
+creation = Add Secret
+creation.name_placeholder = case-insensitive, alphanumeric characters or underscores only, cannot start with GITEA_ or GITHUB_
+creation.value_placeholder = Input any content. Whitespace at the start and end will be omitted.
+creation.success = The secret '%s' has been added.
+creation.failed = Failed to add secret.
+deletion = Remove secret
+deletion.description = Removing a secret will revoke its access to repositories. Continue?
+deletion.success = The secret has been removed.
+deletion.failed = Failed to remove secret.