feat(cloudflare): Allow specifying a custom fetch in Cloudflare transport options

[WalshyDev]

Adds a new transport option to the Cloudflare provider, this allows specifying a custom fetch implementation. This allows for Workers VPC to send into an internal Sentry.

Example usage:

export default Sentry.withSentry(
  (env: Env) => ({
    dsn: env.SENTRY_DSN,
    release: env.VERSION_METADATA.tag ?? env.VERSION_METADATA.id,
    transportOptions: {
      fetch: env.SENTRY_VPC_BRIDGE.fetch.bind(env.SENTRY_VPC_BRIDGE),
    },
  }),
  {
    async fetch(req, env) {
      return new Response("ok");
    },
};

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[Lms24]

Hey, thanks for opening this PR! This makes sense to me on first glance but I'll let @JPeer264 and @AbhiPrasad have the final say.

[AbhiPrasad]

Thanks!

[WalshyDev]

Thank you!