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)

routers/web/user/profile.go

@@ -63,7 +63,7 @@ func Profile(ctx *context.Context) {
 
 	ctx.Data["Title"] = ctx.ContextUser.DisplayName()
 	ctx.Data["PageIsUserProfile"] = true
-	ctx.Data["Owner"] = ctx.ContextUser
+	ctx.Data["ContextUser"] = ctx.ContextUser
 	ctx.Data["OpenIDs"] = openIDs
 	ctx.Data["IsFollowing"] = isFollowing
 

routers/web/user/setting/profile.go

@@ -326,7 +326,7 @@ func Repos(ctx *context.Context) {
 
 		ctx.Data["Repos"] = repos
 	}
-	ctx.Data["Owner"] = ctxUser
+	ctx.Data["ContextUser"] = ctxUser
 	pager := context.NewPagination(count, opts.PageSize, opts.Page, 5)
 	pager.SetDefaultParams(ctx)
 	ctx.Data["Page"] = pager