Consider enabling process recording by default

When trying to run a sample program I expected the run to be recorded. However, it seems that process recording needs explicit enabling with -Dappmap.recording.auto=true; this is documented but it's not very discoverable (especially without any messages from the agent, cf. #284 ). It's not clear to me why this is not on by default.

分别在带有和不带有 -Dappmap.recording.auto=true 的情况下复现示例程序，然后阅读链接的进程记录文档和 issue #284，了解当前行为以及缺失的 agent 消息。完成的标准是：项目对默认记录行为有明确且经过测试的决定，并且文档与该决定一致。