feat: show agent version in UI and CLI (#3709)

This commit adds the ability for agents to set their version upon start.
This is then reported in the UI and CLI.

coderd/database/queries/workspaceagents.sql

@@ -81,3 +81,11 @@ SET
 	updated_at = $4
 WHERE
 	id = $1;
+
+-- name: UpdateWorkspaceAgentVersionByID :exec
+UPDATE
+	workspace_agents
+SET
+	version = $2
+WHERE
+	id = $1;