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>

templates/org/settings/navbar.tmpl

@@ -12,6 +12,9 @@
 		<a class="{{if .PageIsOrgSettingsLabels}}active {{end}}item" href="{{.OrgLink}}/settings/labels">
 			{{.locale.Tr "repo.labels"}}
 		</a>
+		<a class="{{if .PageIsOrgSettingsSecrets}}active {{end}}item" href="{{.OrgLink}}/settings/secrets">
+			{{.locale.Tr "secrets.secrets"}}
+		</a>
 		{{if .EnableOAuth2}}
 		<a class="{{if .PageIsSettingsApplications}}active {{end}}item" href="{{.OrgLink}}/settings/applications">
 			{{.locale.Tr "settings.applications"}}