fix: avoid missed logs when streaming startup logs (#8029)

* feat(coderd,agent): send startup log eof at the end

* fix(coderd): fix edge case in startup log pubsub

* fix(coderd): ensure startup logs are closed on lifecycle state change (fallback)

* fix(codersdk): fix startup log channel shared memory bug

* fix(site): remove the EOF log line

coderd/database/queries/workspaceagents.sql

@@ -146,18 +146,31 @@ 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)
+		workspace_agent_startup_logs (agent_id, created_at, output, level, eof)
 	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(@level :: log_level [ ]) AS level,
+		unnest(@eof :: boolean [ ]) AS eof
 	RETURNING workspace_agent_startup_logs.*;
 
 -- If an agent hasn't connected in the last 7 days, we purge it's logs.