perf(remix-dev/vite): extract route module exports in parallel for route manifest generation + use transformRequest to utilize vite's transform cache

[hi-ogawa]

(These two ideas are independent, so we can evaluate separately. For initial testing, I pushed in one PR, but I'll create two PRs separately later)

1st idea

Not properly tested or benchmarked yet, but it seems doing await getRouteModuleExports(...) in for loop slow down server start up, so I'm experimenting with doing Promise.all instead.
(Regarding this, I was initially looking at server.warmup option https://vitejs.dev/config/server-options#server-warmup, but what it does is more-or-less just triggering transformRequest in parallel (code) and actually server.warmup won't be triggered for child compiler use cases, so I didn't think further about this option.)

2nd idea

Also, while looking at getRouteModuleExports, I thought it might be beneficial to use ViteDevServer.transformRequest API instead of manually transforming code via PluginContainer API. Currently, I needed experimental.skipSsrTransform to make it work, but I also have another idea to not rely on that (see TODO in the code).
Again I haven't tested properly yet, but I'm hoping this might allow utilizing vite's cache (+ auto invalidation?) to save unnecessary transform.
If this idea is sound, then remix's own caching introduced in #7908 to reduce virtual entry invalidation might not be necessary since I think the bottleneck is getDevManifest transforming all route files to extract all exports.

---

To be able to analyze and evaluate perf ideas more systematically, I'm thinking to prepare dummy remix app with many routes and components. For example, It would be something like remix-equivalent of these benchmarks:

• https://github.com/vitejs/vite-benchmark
• https://github.com/yArna/parcel-vs-vite-vs-turbopack-hmr

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[hi-ogawa]

Superseded by independent PRs

• perf(remix-dev/vite): extract route module exports in parallel #8111
• perf(remix-dev/vite): use transformRequest for route exports anlaysis to utilize Vite's caching #8113