Only log experiments warning if user actually opted in to an experiment(s)

[sophiabits]

Currently if you have a Next config like the following:

module.exports = {
  experimental: {},
},

You are presented with the warning for experimental features, even though you haven't actually enabled any experiments. This PR checks there's at least one key in the experimental object before logging the warning.

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
buildDuration	14.8s	14.7s	-121ms
buildDurationCached	5.8s	5.8s	⚠️ +18ms
nodeModulesSize	359 MB	359 MB	⚠️ +103 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.084	3.021	-0.06
/ avg req/sec	810.57	827.46	+16.89
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.296	1.298	0
/error-in-render avg req/sec	1929.72	1926.46	⚠️ -3.26

Client Bundles (main, webpack, commons)

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42 kB	42 kB	✓
main-HASH.js gzip	27.9 kB	27.9 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	71.5 kB	71.5 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
_app-HASH.js gzip	1.36 kB	1.36 kB	✓
_error-HASH.js gzip	194 B	194 B	✓
amp-HASH.js gzip	312 B	312 B	✓
css-HASH.js gzip	326 B	326 B	✓
dynamic-HASH.js gzip	2.57 kB	2.57 kB	✓
head-HASH.js gzip	350 B	350 B	✓
hooks-HASH.js gzip	919 B	919 B	✓
image-HASH.js gzip	5.05 kB	5.05 kB	✓
index-HASH.js gzip	263 B	263 B	✓
link-HASH.js gzip	2.26 kB	2.26 kB	✓
routerDirect..HASH.js gzip	321 B	321 B	✓
script-HASH.js gzip	383 B	383 B	✓
withRouter-HASH.js gzip	318 B	318 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	14.7 kB	14.7 kB	✓

Client Build Manifests

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
_buildManifest.js gzip	460 B	460 B	✓
Overall change	460 B	460 B	✓

Rendered Page Sizes

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	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	✓

---

Default Build with SWC (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
buildDuration	17.3s	17.5s	⚠️ +243ms
buildDurationCached	5.9s	5.9s	⚠️ +31ms
nodeModulesSize	359 MB	359 MB	⚠️ +103 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.048	3	-0.05
/ avg req/sec	820.1	833.23	+13.13
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.35	1.266	-0.08
/error-in-render avg req/sec	1852.2	1975.13	+122.93

Client Bundles (main, webpack, commons)

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.1 kB	42.1 kB	✓
main-HASH.js gzip	27.9 kB	27.9 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	71.7 kB	71.7 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
_app-HASH.js gzip	1.35 kB	1.35 kB	✓
_error-HASH.js gzip	180 B	180 B	✓
amp-HASH.js gzip	305 B	305 B	✓
css-HASH.js gzip	321 B	321 B	✓
dynamic-HASH.js gzip	2.56 kB	2.56 kB	✓
head-HASH.js gzip	342 B	342 B	✓
hooks-HASH.js gzip	911 B	911 B	✓
image-HASH.js gzip	5.08 kB	5.08 kB	✓
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	2.28 kB	2.28 kB	✓
routerDirect..HASH.js gzip	314 B	314 B	✓
script-HASH.js gzip	375 B	375 B	✓
withRouter-HASH.js gzip	309 B	309 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	14.7 kB	14.7 kB	✓

Client Build Manifests

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
_buildManifest.js gzip	459 B	459 B	✓
Overall change	459 B	459 B	✓

Rendered Page Sizes

	vercel/next.js canary	sophiabits/next.js fix-excessive-experiment-warning	Change
index.html gzip	533 B	533 B	✓
link.html gzip	547 B	547 B	✓
withRouter.html gzip	527 B	527 B	✓
Overall change	1.61 kB	1.61 kB	✓

Commit: 1beb685