fix: tree-shake Node.js code from browser bundles

[joshuaellis]

Description

ENV_TARGET exists in the @module-federation/sdk package to infer tree shaking e.g. if you set it to web then the node branches will be eliminated in theory (there's a PR to change this from func to constant to improve the tree-shaking see Notes section). We now have a target option that will deliver this to the rest of the setup correctly, it falls back to web if not set unless build.ssr is set in which we set it to node these defaults align with vite's default behaviours.

Converts the virtual modules to be ESM in build mode to enable rollup to tree-shake more effectively, however Dev mode still uses CJS because syntheticNamedExports are not respected since vite doesn't use rollup for dev & import { useState } from 'react' would thereby fail. This also seems to be some work required to support vite7 identified in #369 which is nice.

Related Issues

• resolves [Bug]: NodeJS vm code + 'eval' needlessly included in web bundle (Causing CSP errors) #274

Notes

This PR requires:

• test(integration): cover remote & host build, CSS bundling and shared deps #406 to be merged first
  Related PRS:
• fix(sdk): add isBrowserEnvValue for tree-shaking core#4454 to be merged & published so we can update this repo – when this is done, i'll do a separate PR.