Clarify permission "HasAccess" behavior (#30585)

Follow #30495

"HasAccess" behavior wasn't clear, to make it clear:

* Use a new name `HasAnyUnitAccess`, it will be easier to review related
code and permission problems.
* Separate everyone access mode to a separate field, then all calls to
HasAccess are reverted to old behavior before #30495.
* Add new tests.

---------

Co-authored-by: Giteabot <teabot@gitea.io>

tests/integration/api_repo_test.go

@@ -222,7 +222,7 @@ func TestAPISearchRepo(t *testing.T) {
 					assert.Len(t, repoNames, expected.count)
 					for _, repo := range body.Data {
 						r := getRepo(t, repo.ID)
-						hasAccess, err := access_model.HasAccess(db.DefaultContext, userID, r)
+						hasAccess, err := access_model.HasAnyUnitAccess(db.DefaultContext, userID, r)
 						assert.NoError(t, err, "Error when checking if User: %d has access to %s: %v", userID, repo.FullName, err)
 						assert.True(t, hasAccess, "User: %d does not have access to %s", userID, repo.FullName)