chore: rework msw usage to support more runtimes

[frederikprijck]

Description

• Replace msw/node with a custom mock-http.ts fetch-patching implementation across all packages (auth0-auth-js, auth0-server-js, auth0-api-js) so tests run on Bun, Deno, and Cloudflare Workers without Node.js
  HTTP interceptors
  • Add a BroadcastChannel stub polyfill for the Workers runtime, where MSW imports it unconditionally but it is not available as a global
  • Update vitest.config.workers.ts and wrangler.toml in each package to wire up the new test utilities

References

N/A

Testing

• This change adds test coverage for new/changed/fixed functionality

Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not the default branch

[frederikprijck]

Need to revert these changes prior to merge