feat: upgrade fern CLI, all generator versions (major) + GH workflow fix

[fern-support]

Description

Breaking changes:

• Upgraded fern CLI: requires minimum generator versions now
• Python 5.0.0: Min Python version raised from 3.8 to 3.10
• Ruby 1.0.0: Complete rewrite of the generator. Backwards compatible with existing configs/gem names/modules, but generated code structure is entirely new.
• PHP 2.0.0: Guzzle is no longer a hard dependency (moved to suggest/require-dev).
• Swift 0.28.0: Discriminated unions now use direct associated values instead of synthesized nested wrapper structs. Changes the shape of union types in generated code.

No breaking changes for TypeScript, Go, C#.

Read more on the changes here:
https://buildwithfern.com/learn/cli-api-reference/cli-reference/changelog#400
https://buildwithfern.com/learn/sdks/overview (changelog for each language)

Testing Steps

Generated each SDK locally and ensured each SDK compiles and passes tests

[github-actions]

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