Refactor file_upload to avoid janus dep

[bdraco]

Proposed change

Refactor file_upload to avoid janus requirement

The goal is to avoid the import cost of janus since file_upload is a dep of frontend

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
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[home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as it has been labeled with an integration (file_upload) you are listed as a code owner for? Thanks!

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[MartinHjelmare]

The PR description doesn't say what the import cost is.

[bdraco]

It was ~1.2s on my green, and ~0.4s on my more powerful x86_64 system