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>

services/context/repo.go

@@ -374,8 +374,7 @@ func repoAssignment(ctx *Context, repo *repo_model.Repository) {
 		return
 	}
 
-	// Check access.
-	if !ctx.Repo.Permission.HasAccess() {
+	if !ctx.Repo.Permission.HasAnyUnitAccessOrEveryoneAccess() {
 		if ctx.FormString("go-get") == "1" {
 			EarlyResponseForGoGetMeta(ctx)
 			return