Simplify RenderResult

[devknoll]

We're no longer currently planning on supporting caching for dynamic responses, so we can do some cleaning & simplification:

• Multiplexing can be removed since we only ever subscribe once (via RenderResult.pipe, described below)
• RenderResult.toUnchunkedString can become synchronous since static responses are never chunked
• RenderResult.forEach can become RenderResult.pipe which helps encapsulate some of the details of RenderResult

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall decrease ✓

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
buildDuration	13.5s	13.7s	⚠️ +233ms
buildDurationCached	3.4s	3.3s	-11ms
nodeModulesSize	48.2 MB	48.2 MB	-3.69 kB

Page Load Tests Overall increase ✓

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.665	2.594	-0.07
/ avg req/sec	938.04	963.64	+25.6
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.408	1.388	-0.02
/error-in-render avg req/sec	1776.18	1800.59	+24.41

Client Bundles (main, webpack, commons)

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
745.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.2 kB	42.2 kB	✓
main-HASH.js gzip	23.3 kB	23.3 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	67.2 kB	67.2 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
polyfills-a4..dd70.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
_app-HASH.js gzip	979 B	979 B	✓
_error-HASH.js gzip	194 B	194 B	✓
amp-HASH.js gzip	312 B	312 B	✓
css-HASH.js gzip	329 B	329 B	✓
dynamic-HASH.js gzip	2.67 kB	2.67 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	918 B	918 B	✓
image-HASH.js gzip	4.14 kB	4.14 kB	✓
index-HASH.js gzip	261 B	261 B	✓
link-HASH.js gzip	1.66 kB	1.66 kB	✓
routerDirect..HASH.js gzip	318 B	318 B	✓
script-HASH.js gzip	387 B	387 B	✓
withRouter-HASH.js gzip	320 B	320 B	✓
bb14e60e810b..30f.css gzip	125 B	125 B	✓
Overall change	13 kB	13 kB	✓

Client Build Manifests

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
_buildManifest.js gzip	492 B	492 B	✓
Overall change	492 B	492 B	✓

Rendered Page Sizes

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
index.html gzip	539 B	539 B	✓
link.html gzip	552 B	552 B	✓
withRouter.html gzip	533 B	533 B	✓
Overall change	1.62 kB	1.62 kB	✓

---

Webpack 4 Mode (Increase detected ⚠️)

General Overall decrease ✓

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
buildDuration	10.8s	11s	⚠️ +138ms
buildDurationCached	4.8s	4.5s	-279ms
nodeModulesSize	48.2 MB	48.2 MB	-3.69 kB

Page Load Tests Overall increase ✓

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.623	2.653	⚠️ +0.03
/ avg req/sec	953.15	942.4	⚠️ -10.75
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.465	1.413	-0.05
/error-in-render avg req/sec	1705.99	1768.7	+62.71

Client Bundles (main, webpack, commons)

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
16.HASH.js gzip	186 B	186 B	✓
677f882d2ed8..HASH.js gzip	14.1 kB	14.1 kB	✓
framework.HASH.js gzip	41.9 kB	41.9 kB	✓
main-HASH.js gzip	10.7 kB	10.7 kB	✓
webpack-HASH.js gzip	1.19 kB	1.19 kB	✓
Overall change	68.1 kB	68.1 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
polyfills-a4..dd70.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
_app-HASH.js gzip	964 B	964 B	✓
_error-HASH.js gzip	3.8 kB	3.8 kB	✓
amp-HASH.js gzip	552 B	552 B	✓
css-HASH.js gzip	333 B	333 B	✓
dynamic-HASH.js gzip	2.87 kB	2.87 kB	✓
head-HASH.js gzip	3.06 kB	3.06 kB	✓
hooks-HASH.js gzip	924 B	924 B	✓
index-HASH.js gzip	231 B	231 B	✓
link-HASH.js gzip	1.64 kB	1.64 kB	✓
routerDirect..HASH.js gzip	298 B	298 B	✓
script-HASH.js gzip	3.03 kB	3.03 kB	✓
withRouter-HASH.js gzip	295 B	295 B	✓
30809af5c834..565.css gzip	125 B	125 B	✓
Overall change	18.1 kB	18.1 kB	✓

Client Build Manifests

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
_buildManifest.js gzip	500 B	500 B	✓
Overall change	500 B	500 B	✓

Rendered Page Sizes

	vercel/next.js canary	azukaru/next.js x-simplify-render	Change
index.html gzip	585 B	585 B	✓
link.html gzip	597 B	597 B	✓
withRouter.html gzip	578 B	578 B	✓
Overall change	1.76 kB	1.76 kB	✓

Commit: cf49eac