Create pod eviction concept and glossary entries

- Created glossary entries for manual and kubelet eviction
  - Created node-pressure-eviction.md and api-eviction.md
  - Merged content from eviction-policy.md and out-of-resource.md
  - Added note to kube-scheduler about node conditions
  - Deleted eviction-policy and out-of-resource.md
  - Redirected old topics
  - Change topic weights

content/en/docs/reference/glossary/api-eviction.md

@@ -0,0 +1,22 @@
+---
+title: API-initiated eviction
+id: api-eviction
+date: 2021-04-27
+full_link: /docs/concepts/scheduling-eviction/pod-eviction/#api-eviction
+short_description: >
+  API-initiated eviction is the process by which you use the Eviction API to create an
+  Eviction object that triggers graceful pod termination.
+aka:
+tags:
+- operation
+---
+API-initiated eviction is the process by which you use the [Eviction API](/docs/reference/generated/kubernetes-api/{{<param "version">}}/#create-eviction-pod-v1-core)
+to create an `Eviction` object that triggers graceful pod termination.
+
+<!--more-->
+
+You can request eviction either by directly calling the Eviction API 
+using a client of the kube-apiserver, like the `kubectl drain` command. 
+When an `Eviction` object is created, the API server terminates the Pod. 
+
+API-initiated eviction is not the same as [node-pressure eviction](/docs/concepts/scheduling-eviction/eviction/#kubelet-eviction).