perf(ivy): improve Uglify configuration in hello world integration test

[marclaval]

This PRs implements suggestions from #21880
The bundle size is now 9.8k (vs ~8k with Closure)

[trotyl]

Since build-optimizer has provided its own rollup plugin, would it be better to use that official one instead of some 3rd-party not-well-maintained naive implementation?

_{Would require next build-optimizer, so could be done in separate PR.}

[alexeagle]

@trotyl has a good point - @marclaval do we even need this integration test anymore, since we're measuring bundles using "unit tests" in packages/core/test/bundling ?

[marclaval]

@trotyl I've opened a PR to use the official plugin: #22121
@alexeagle From Igor's comment (#21940 (comment)), I understand we should keep it to see the trend

[alexeagle]

I think we should get the trend from Daniel15/BuildSize#7 instead - need to evaluate that and we can tear down ours once we're satisfied with results and stability.

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