NodeJS Compat: Process Compat via Separate Implementation

[guybedford]

This reincludes the unrevert of the original PR from #4271 and all of its features, along with the unrevert of the compatibility flag introduced in #4350.

Then to ensure compatibility, instead of exporting undefined named exports for process features when not using the enable_nodejs_process_v2 compatibility flag, two entirely separate process implementations are provided as internal modules - node-internal:public_process for the new implementation and node-internal:legacy_process for the former implementation. Implementation internals are then shared as suitable through the internal process module as well.

Then in the resolver, we detect node:process and process imports and direct those to either node-internal:public_process or node-internal:legacy_process depending on the compat flag. process.getBuiltinModule also has a similar switch logic along with the global getter function for globalThis.process.

Tests are added for the legacy process module to ensure it does not contain unexpected properties. In this way, full compatibility is maintained for all users not using the new process implementation.

New process features remain identical to the original summary in #4271.

Stdio and FS integrations remain pending for removing experimental.

While working on this I noticed the Node.js LTS version already bumped a minor - Claude was able to cook up a script to bump this automatically for us which is also added here as just update-reported-node-version for convenience.

[github-actions]

The generated output of @cloudflare/workers-types matches the snapshot in types/generated-snapshot 🎉

[codspeed-hq]

CodSpeed Performance Report

Merging #4446 will not alter performance

_{Comparing gbedford/process-compat-flag-v2 (566b232) with main (0bf8308)}

Summary

✅ 10 untouched benchmarks