Remove dead cacheComponents web streams path (#93944)
### What?
Remove the cacheComponents + web streams rendering branches from
`app-render`.
### Why?
`cacheComponents` does not support the edge runtime, and Node streams
are now always-on for the Node.js runtime in the parent PR. That makes
the cacheComponents web-stream branches dead code.
### How?
- Collapse cacheComponents staged RSC rendering to the Node-stream
implementation.
- Remove the web-stream cacheComponents helper functions and
static-stage byte counter.
- Keep the ordinary non-cacheComponents web-stream paths for
edge/runtime compatibility.
### Verification
- `pnpm --filter=next types`
- `pnpm --filter=next build`
- `pnpm test-start-webpack test/e2e/app-dir/app/standalone.test.ts`
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