Switch language name 'zh' to 'zh-cn'

This is the first step to rename 'zh' to 'zh-cn'. There are several reasons why we rename the language name.

- The upstream docsy theme changed the language name, leading to many warnings during site build;
  The side-effect is that the i18n strings are no longer working.
- We believe renaming the language is the right thing to do, because this move can make room for other variants of Chinese language, such as 'zh-tw', 'zh-sg' etc.

There would be several follow-ups to this PR, such as fixing the intra-site links, adding redirects etc.

We will lock up changes to zh/zh-cn pages for the moment, until this one gets in.

This PR is based on commit cdad0a7342.

content/zh-cn/docs/reference/glossary/finalizer.md

@@ -0,0 +1,65 @@
+---
+title: Finalizer
+id: finalizer
+date: 2021-07-07
+full_link: /zh/docs/concepts/overview/working-with-objects/finalizers/
+short_description: >
+  一个带有命名空间的键，告诉 Kubernetes 等到特定的条件被满足后，
+  再完全删除被标记为删除的资源。
+aka: 
+tags:
+- fundamental
+- operation
+---
+
+<!--
+---
+title: Finalizer
+id: finalizer
+date: 2021-07-07
+full_link: /zh/docs/concepts/overview/working-with-objects/finalizers/
+short_description: >
+  A namespaced key that tells Kubernetes to wait until specific conditions are met
+  before it fully deletes an object marked for deletion.
+aka: 
+tags:
+- fundamental
+- operation
+-->
+
+
+<!--
+Finalizers are namespaced keys that tell Kubernetes to wait until specific
+conditions are met before it fully deletes resources marked for deletion.
+Finalizers alert {{<glossary_tooltip text="controllers" term_id="controller">}}
+to clean up resources the deleted object owned.
+-->
+Finalizer 是带有命名空间的键，告诉 Kubernetes 等到特定的条件被满足后，
+再完全删除被标记为删除的资源。
+Finalizer 提醒{{<glossary_tooltip text="控制器" term_id="controller">}}清理被删除的对象拥有的资源。
+<!--more-->
+
+<!--
+When you tell Kubernetes to delete an object that has finalizers specified for
+it, the Kubernetes API marks the object for deletion by populating `.metadata.deletionTimestamp`,
+and returns a `202` status code (HTTP "Accepted"). The target object remains in a terminating state while the
+control plane, or other components, take the actions defined by the finalizers.
+After these actions are complete, the controller removes the relevant finalizers
+from the target object. When the `metadata.finalizers` field is empty,
+Kubernetes considers the deletion complete.
+-->
+当你告诉 Kubernetes 删除一个指定了 Finalizer 的对象时，
+Kubernetes API 通过填充 `.metadata.deletionTimestamp` 来标记要删除的对象，
+并返回`202`状态码 (HTTP "已接受") 使其进入只读状态。
+此时控制平面或其他组件会采取 Finalizer 所定义的行动，
+而目标对象仍然处于终止中（Terminating）的状态。
+这些行动完成后，控制器会删除目标对象相关的 Finalizer。
+当 `metadata.finalizers` 字段为空时，Kubernetes 认为删除已完成。
+
+<!--
+You can use finalizers to control {{<glossary_tooltip text="garbage collection" term_id="garbage-collection">}}
+of resources. For example, you can define a finalizer to clean up related resources or
+infrastructure before the controller deletes the target resource.
+-->
+你可以使用 Finalizer 控制资源的{{<glossary_tooltip text="垃圾收集" term_id="garbage-collection">}}。
+例如，你可以定义一个 Finalizer，在删除目标资源前清理相关资源或基础设施。