Add Modal worker support to serverless worker deployment CLI

[harish-narayanappa-10]

What changed?

• Add Modal compute-provider flags to Worker Deployment Version create and update commands.
• Require application, function, and environment; support optional workspace and application versions.
• Pair Modal invocation with the no-sync scaler and reject conflicting provider flags.

Checklist

• Modal flags follow provider API concepts and have no short aliases.
• Help text includes functional create and update examples.
• Unit and functional tests cover validation, payloads, and provider switching.

Manual tests

Not manually tested; automated tests cover validation, request construction, conflicts, and provider switching.

[CLAassistant]

All committers have signed the CLA.