feat(nextjs): Add `cache_origin` span links to `use cache` hit spans (#24821)

A `"use cache"` hit tells you nothing about where the value came from.
This PR connects the two traces: a `cache.get` hit span now carries a
span link (`sentry.link.type: 'cache_origin'`) to the `cache.put` span
of the request that filled the entry.

This covers cached functions, components, and layouts that Next reads
through its cache handlers at request time. That's `"use cache"` in
route handlers and in dynamically rendered pages.


Successful cache fills are remembered in a bounded per-process `LRUMap`.
When the cache origin is unknown, the hit span gets no link.


Closes https://github.com/getsentry/sentry-javascript/issues/24294
Linear:
https://linear.app/getsentry/issue/JS-3656/link-cache-hits-to-the-trace-that-filled-the-cache-entry