[API] generalize list header (#16551)

* Add info about list endpoints to CONTRIBUTING.md

* Let all list endpoints return X-Total-Count header 

* Add TODOs for GetCombinedCommitStatusByRef

* Fix models/issue_stopwatch.go

* Rrefactor models.ListDeployKeys

* Introduce helper func and use them for SetLinkHeader related func

models/org_team_test.go

@@ -286,7 +286,7 @@ func TestGetTeamMembers(t *testing.T) {
 func TestGetUserTeams(t *testing.T) {
 	assert.NoError(t, PrepareTestDatabase())
 	test := func(userID int64) {
-		teams, err := GetUserTeams(userID, ListOptions{})
+		teams, _, err := SearchTeam(&SearchTeamOptions{UserID: userID})
 		assert.NoError(t, err)
 		for _, team := range teams {
 			AssertExistsAndLoadBean(t, &TeamUser{TeamID: team.ID, UID: userID})