refactor: replace startup script logs EOF with starting/ready time (#8082)

This commit reverts some of the changes in #8029 and implements an
alternative method of keeping track of when the startup script has ended
and there will be no more logs.

This is achieved by adding new agent fields for tracking when the agent
enters the "starting" and "ready"/"start_error" lifecycle states. The
timestamps simplify logic since we don't need understand if the current
state is before or after the state we're interested in. They can also be
used to show data like how long the startup script took to execute. This
also allowed us to remove the EOF field from the logs as the
implementation was problematic when we returned the EOF log entry in the
response since requesting _after_ that ID would give no logs and the API
would thus lose track of EOF.

coderd/database/queries/workspaceagents.sql

@@ -87,11 +87,24 @@ SET
 WHERE
 	id = $1;
 
+-- name: GetWorkspaceAgentLifecycleStateByID :one
+SELECT
+	lifecycle_state,
+	started_at,
+	ready_at
+FROM
+	workspace_agents
+WHERE
+	id = $1;
+
+
 -- name: UpdateWorkspaceAgentLifecycleStateByID :exec
 UPDATE
 	workspace_agents
 SET
-	lifecycle_state = $2
+	lifecycle_state = $2,
+	started_at = $3,
+	ready_at = $4
 WHERE
 	id = $1;
 
@@ -146,31 +159,18 @@ WHERE
 		id > @created_after
 	) ORDER BY id ASC;
 
--- name: GetWorkspaceAgentStartupLogsEOF :one
-SELECT CASE WHEN EXISTS (
-	SELECT
-		*
-	FROM
-		workspace_agent_startup_logs
-	WHERE
-		agent_id = $1
-		AND eof = true
-	LIMIT 1
-) THEN TRUE ELSE FALSE END;
-
 -- name: InsertWorkspaceAgentStartupLogs :many
 WITH new_length AS (
 	UPDATE workspace_agents SET
 	startup_logs_length = startup_logs_length + @output_length WHERE workspace_agents.id = @agent_id
 )
 INSERT INTO
-		workspace_agent_startup_logs (agent_id, created_at, output, level, eof)
+		workspace_agent_startup_logs (agent_id, created_at, output, level)
 	SELECT
 		@agent_id :: uuid AS agent_id,
 		unnest(@created_at :: timestamptz [ ]) AS created_at,
 		unnest(@output :: VARCHAR(1024) [ ]) AS output,
-		unnest(@level :: log_level [ ]) AS level,
-		unnest(@eof :: boolean [ ]) AS eof
+		unnest(@level :: log_level [ ]) AS level
 	RETURNING workspace_agent_startup_logs.*;
 
 -- If an agent hasn't connected in the last 7 days, we purge it's logs.