Use tencent mirror source for dependency proxy to replace azure source

What does this MR do and why?

Use tencent mirror source for dependency proxy to replace azure source

Related issue: https://jihulab.com/gitlab-cn/gitlab/-/issues/3848

Related MR: !1443 (merged)

Because Azure will stop the support for JH, so we switch to tencent mirror source.

Use new feature flag dependency_proxy_use_tencent_source for it.