Typegen: merge configured cacheLife profiles into next/cache types

Next.js Change

Commit: f464e32 (#98252)

What changed

Next.js moved configured cacheLife profile declarations to an augmentation of next/cache rather than a standalone ambient module that shadows the package types. It adds a CacheLifeProfiles interface to next/cache and constrains string profile names when that interface is augmented, while retaining the object-form cacheLife() overload.

Impact on vinext

vinext implements the next/cache API and Cache Components configuration. Its generated or declared types should preserve all existing next/cache exports while providing typed custom cacheLife profile names from project configuration.

Acceptance criteria

• Declare an augmentable CacheLifeProfiles interface in vinext's next/cache types.
• Restrict string cacheLife() and unstable_cacheLife() profile arguments to configured profiles when present, while allowing arbitrary strings when none are configured.
• Keep the object-form cacheLife() overload available.
• Generate a module augmentation, not a standalone declaration that shadows other next/cache exports.
• Add type-level coverage for valid configured profiles, rejected unknown profiles, and existing next/cache exports.

References

• https://github.com/vercel/next.js/commit/f464e32ec092c5a00c967e64cba40121a2992224