[Metrics] Support cloudflare workers

[ale-cota]

Problem Statement

The different JS functions can't be used in a cloudflare worker environment where I/O is not allowed outside the request, it fails with:

Error: Disallowed operation called within global scope. Asynchronous I/O (ex: fetch() or connect()), setting a timeout, and generating random values are not allowed within global scope. To fix this error, perform this operation within a handler. https://developers.cloudflare.com/workers/runtime-apis/handlers/

Solution Brainstorm

Afraid I don't have any bright ideas here. Here is the original request: getsentry/sentry#64195 (comment)

[Lms24]

This ties in with general CF worker support which we still need to tackle. Tracked in #2484 and more generally in #5611

[AbhiPrasad]

With the changes to metrics to use span attributes, this is a won't do now.