fix(bundler-plugins): Keep debug IDs on Vite source maps after the preload rewrite (#24920)

With `sourcemaps.disable: 'disable-upload'`, Vite builds shipped some
source maps without a debug ID. Vite's own `generateBundle` step
rewrites every chunk with a dynamic import to add module preloading,
regenerates that chunk's source map and overwrites the `.map` asset.
This runs after the Sentry plugin's `pre` hook stamped the map, so the
stamp is lost. Sentry then cannot match the map to the chunk.

`sentryVitePlugin()` now also returns a `post` plugin that re-stamps the
maps in a `post` `generateBundle` hook. It leaves the chunk code alone,
so file hashes stay valid. Reproduced on Vite 7.3 and 8.0, and the new
integration fixture fails without the fix.

Split out of #23665 by @chen-anders.

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Co-authored-by: Anders Chen <anders@wistia.com>