Optimize root domain search through api

[keryfan]

No description provided.

[github-actions]

Welcome
First thing: don't send PR to the master branch, please send to the dev branch instead.
Please make sure you've read our DNS API Dev Guide and DNS-API-Test.
Then reply on this message, otherwise, your code will not be reviewed or merged.
Please also make sure to add/update the usage here: https://github.com/acmesh-official/acme.sh/wiki/dnsapi2
We look forward to reviewing your Pull request shortly ✨
注意: 必须通过了 DNS-API-Test 才会被 review. 无论是修改, 还是新加的 dns api, 都必须确保通过这个测试.

[keryfan]

I have read the guide. This PR just adds filtering to root-domains check to speed-up the process, the rest of the code is same.

[Neilpang]

please follow the dns api test:
https://github.com/acmesh-official/acme.sh/wiki/DNS-API-Test

Any changes to the dns api hook must be verified by the dns api test.