Improve tensor point cloud io

[ZhengyuDiao]

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[update-docs[bot]]

Thanks for submitting this pull request! The maintainers of this repository would appreciate if you could update the CHANGELOG.md based on your changes.

[ZhengyuDiao]

Now the other files io in tensor module use double as default, so the tests of io also use double as default. If I use float as default in FileTXT, it cannot pass the tests. I think we may keep double as default this time and modify the default dtype from double to float in the relevant files in next pr. What do you think about it? @yxlao