fix: create parent dir if not present in the ouput param path

[Vipulkr1698]

When using the command of the below format
poetry export -o package/lib/requirements.txt

In the above example, if the package/lib directory doesn't exist, the above command would fail. With the fix, the tool would create all the necessary intermediate folders to the file path provided and export the dependencies to the file provided.

[sonarcloud]

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[neersighted]

Pathlib functions should be used instead of os.path; e.g. output.parent. However, that isn't sufficient -- this is too naive. Tests should be written, which should reveal where more thought is needed.

Also, this is very clearly a new feature and not a fix; Poetry has never claimed to create these paths before.