Fix missing _app component of AppTree in gIP context

[huozhi]

Bug

The custom app is missing in the ctx.AppTree that causing the issue, it was accidently missed in custom _app.server pr #35666

Fixes #36198

• Related issues linked using fixes #number
• Integration tests added
• Errors have helpful link attached, see contributing.md

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
buildDuration	15.8s	15.3s	-581ms
buildDurationCached	6.3s	5.5s	-756ms
nodeModulesSize	485 MB	485 MB	⚠️ +480 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.161	3.019	-0.14
/ avg req/sec	790.99	828.13	+37.14
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.381	1.326	-0.05
/error-in-render avg req/sec	1810.77	1885.49	+74.72

Client Bundles (main, webpack)

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
925.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42 kB	42 kB	✓
main-HASH.js gzip	28.3 kB	28.3 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	72 kB	72 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
_app-HASH.js gzip	1.36 kB	1.36 kB	✓
_error-HASH.js gzip	192 B	192 B	✓
amp-HASH.js gzip	309 B	309 B	✓
css-HASH.js gzip	327 B	327 B	✓
dynamic-HASH.js gzip	3.04 kB	3.04 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	920 B	920 B	✓
image-HASH.js gzip	5.74 kB	5.74 kB	✓
index-HASH.js gzip	263 B	263 B	✓
link-HASH.js gzip	2.36 kB	2.36 kB	✓
routerDirect..HASH.js gzip	320 B	320 B	✓
script-HASH.js gzip	392 B	392 B	✓
withRouter-HASH.js gzip	319 B	319 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	16 kB	16 kB	✓

Client Build Manifests

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
_buildManifest.js gzip	461 B	461 B	✓
Overall change	461 B	461 B	✓

Rendered Page Sizes

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
index.html gzip	530 B	530 B	✓
link.html gzip	544 B	544 B	✓
withRouter.html gzip	524 B	524 B	✓
Overall change	1.6 kB	1.6 kB	✓

---

Default Build with SWC (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
buildDuration	17.8s	16.8s	-946ms
buildDurationCached	5.7s	5.7s	⚠️ +61ms
nodeModulesSize	485 MB	485 MB	⚠️ +480 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.258	2.957	-0.3
/ avg req/sec	767.46	845.41	+77.95
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.433	1.267	-0.17
/error-in-render avg req/sec	1744.59	1972.62	+228.03

Client Bundles (main, webpack)

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
925.HASH.js gzip	178 B	178 B	✓
framework-HASH.js gzip	42.3 kB	42.3 kB	✓
main-HASH.js gzip	28.7 kB	28.7 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	72.6 kB	72.6 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
_app-HASH.js gzip	1.35 kB	1.35 kB	✓
_error-HASH.js gzip	179 B	179 B	✓
amp-HASH.js gzip	313 B	313 B	✓
css-HASH.js gzip	325 B	325 B	✓
dynamic-HASH.js gzip	3.02 kB	3.02 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	921 B	921 B	✓
image-HASH.js gzip	5.78 kB	5.78 kB	✓
index-HASH.js gzip	261 B	261 B	✓
link-HASH.js gzip	2.44 kB	2.44 kB	✓
routerDirect..HASH.js gzip	322 B	322 B	✓
script-HASH.js gzip	393 B	393 B	✓
withRouter-HASH.js gzip	317 B	317 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	16.1 kB	16.1 kB	✓

Client Build Manifests

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
_buildManifest.js gzip	457 B	457 B	✓
Overall change	457 B	457 B	✓

Rendered Page Sizes

	vercel/next.js canary	huozhi/next.js fix/default-app-tree	Change
index.html gzip	532 B	532 B	✓
link.html gzip	545 B	545 B	✓
withRouter.html gzip	526 B	526 B	✓
Overall change	1.6 kB	1.6 kB	✓

Commit: 77b56b3