feat(build): Core packages into single output files

[timfish]

Ref #7859

Before making the changes in this PR, the following code:

console.time('import sdk');
const pkg = await import('@sentry/nextjs');
console.assert(pkg != undefined);
console.timeEnd('import sdk');

Outputs around 75ms with node v18.17.0.

After the changes in this PR, the time came down to around 55ms, so around a 30% improvement for Node.js loading.

I suspect there will be greater improvements for bundlers but I've not tested that yet.

[timfish]

It's worth noting that once nextjs migrates to the otel node package, this is likely to regress significantly.

Even when bundled to a single file, the otel node SDK on its own takes ~125ms to import. This is in comparison to ~40ms for the old Node SDK.

Without looking into this too much, I guess it's all the otel imports and perhaps even some side effects they introduce?

[AbhiPrasad]

Even when bundled to a single file, the otel node SDK on its own takes ~125ms to import. This is in comparison to ~40ms for the old Node SDK.

This matches my personal testing, it increasingly seems like we have to contribute upstream to help improve situation there.

[AbhiPrasad]

I guess this has an adverse affect on bundle analyzer tools right? Harder to tell via the visualizations what is problematic.

[timfish]

I guess this has an adverse affect on bundle analyzer tools right?

Yep, I guess you'll only see module level detail