Support routing metrics to different DSNs in MFE setup

[chargome]

Currently metrics will be sent on the client that lives on the current scope:

sentry-javascript/packages/core/src/metrics/internal.ts

Line 163 in 2f0d9dc

const currentScope = options?.scope ?? getCurrentScope();

We want to provide an easy way for routing metrics to different DSNs just like we do with errors.

[linear]

JS-1518