cli/command/container: inline parseWindowsDevice, and minor cleanups

[thaJeztah]

It's not parsing anything, so we may as well inline it to be more clear what's done.

- What I did

- How I did it

- How to verify it

- Human readable description for the release notes

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

:x: Patch coverage is 72.22222% with 5 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cli/command/container/opts.go	0.00%	5 Missing :warning:

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