Support some basic file-system operations for kotlinx.io.files.Path

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kotlinx.io.files.Path was added only to provide some basic operations with files and it'll be eventually replaced with proper filesystem API.

However, until it happens, there should be a way to perform some basic filesystem operations.
Following need to be added:

• delete files
• check file/directory existence
• move files atomically
• mkdirs

[fzhinkin]

Also need a way to get a path to temporary dir