Sleep longer if request speed is over github limitation (#9335)

* Sleep longer if request speed is over github limitation

* improve code

* remove unused code

* fix lint

* Use github's rate limit remain value to determine how long to sleep

* Save reset time when finished github api request

* fix bug

* fix lint

* Add context.Context for sleep

* fix test

* improve code

* fix bug and lint

* fix import order

modules/migrations/git.go

@@ -5,6 +5,8 @@
 package migrations
 
 import (
+	"context"
+
 	"code.gitea.io/gitea/modules/migrations/base"
 )
 
@@ -28,6 +30,10 @@ func NewPlainGitDownloader(ownerName, repoName, remoteURL string) *PlainGitDownl
 	}
 }
 
+// SetContext set context
+func (g *PlainGitDownloader) SetContext(ctx context.Context) {
+}
+
 // GetRepoInfo returns a repository information
 func (g *PlainGitDownloader) GetRepoInfo() (*base.Repository, error) {
 	// convert github repo to stand Repo