Fix unclear "Owner" concept (#24233)

Some user/org pages use `Owner` variable. It's an incorrect concept
since year 2016: what is a user's owner?

Actually, new code is right: use `ContextUser`.

This PR cleans all legacy "Owner" variables.

## Screenshots for related pages and test results

All pages are as before:

### `web/org/home.go`


![image](https://user-images.githubusercontent.com/2114189/233366687-a3643025-1f78-474d-a901-deea35b72f4d.png)

### `web/user/profile.go`


![image](https://user-images.githubusercontent.com/2114189/233366812-2e5c2fbc-3f78-44e7-88c1-ec2f612c241e.png)

### `web/user/setting/profile.go`


![image](https://user-images.githubusercontent.com/2114189/233366928-7a1e52c9-b400-4379-a4be-af06a853c5fa.png)

templates/user/overview/header.tmpl

@@ -67,8 +67,8 @@
 			{{if not .DisableStars}}
 				<a class='{{if eq .TabName "stars"}}active {{end}}item' href="{{.ContextUser.HomeLink}}?tab=stars">
 					{{svg "octicon-star"}} {{.locale.Tr "user.starred"}}
-					{{if .Owner.NumStars}}
-						<div class="ui primary label">{{.Owner.NumStars}}</div>
+					{{if .ContextUser.NumStars}}
+						<div class="ui primary label">{{.ContextUser.NumStars}}</div>
 					{{end}}
 				</a>
 			{{else}}