Remove DWO

Related: Use devfile gem in spike branch (gitlab-org/gitlab#392492 - closed)

Done:

• Change informer from devworkspace to deployment.
• Use labels to filter resources while creating informers. This makes sures each agent is only watching over resources for which it is responsible. Nothing more.
• Draining of applier events made async. This ensures that the agentk polling loop is not blocked in case of applying a deployment which will fail(CrashBackLoopOff).
• Removed actual state calculation from agentk. Agentk will only be responsible for sending over the resource metadata and rails will calculate the actual state. This makes the agentk more "dumb", as desired.
• Removed the Failure field from WorkspaceAgentInfo since it is not used anywhere in agentk or rails.
• Send nil in LatestK8sDevWorkspaceInfo if the workspace is terminated since there is no resource metadata to send(as it has been terminated). The actual state of terminated is calculated on rails side when it sees this field as nil.

TODO: Will be done in a follow-up MR since that has to be co-ordinated with rails changes and the rails MR is already too large.

• Rename all variables from devworkspace to deployment
• Remove references to devworkspacerouting