refactor bundling lifecycle and resource optimizations

[thescientist13]

Type of Change

• New Feature Request
• Documentation / Website
• Improvement / Suggestion
• Bug
• Other (please clarify below)

Summary

Our rollup.config.js is doing a LOT of work that is potentially being duplicated not only in this file, but later on in our HTML optimization step, (where scripts and things are swapped out / updated). Since the beginning I had felt / wanted to refactor this because it felt wildly inefficient and redundant in a few places, but performed "well enough", but now I think this is a contributing factor to the benchmarking hangups potentially surfacing as part of #970 .

Details

I think we could simplify some of this a a lot. Things that seems like good opportunities to check for / refactor:

• Capture resources (e.g. <script> / <style> / <link> tag) once and just share that list with everything that needs it
• Reduce repeated looping through HTML files, maybe only doing them in the HTML optimization phase
• Optimize resources in parallel
• See if we can completely elimination needing Rollup specific configs and just rely in our resource plugins entirely - Rollup plugin is a leaky abstraction #550
• See if helps align on support resource plugin based transformations for standard module formats (ex: import JSON, CSS) for SSR #878 (maybe if we are using custom resources, we don't need to provide plugins to Rollup?)

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Even if it doesn't improve benchmarking that much, I think the refactoring opportunity alone is worth it and getting even a little more decoupled from any one bundler fits within the spirit of the project.