feat(browser): Add bundle.mfe CDN bundle for micro frontends - #26114

Why: #17309 asks for one CDN script for micro frontends instead of bundle.min.js plus the multiplexedtransport.min.js and modulemetadata.min.js addons, and the thread settled on a single errors-only combination. bundle.mfe.min.js is the errors-only bundle plus makeMultiplexedTransport and moduleMetadataIntegration. It adds about 650 bytes gzipped to bundle.min.js (size-limit: 32,838 vs 32,194 bytes), while the two addon scripts are about 2 KB gzipped and two extra requests.

How to review: The entry is packages/browser/src/index.bundle.mfe.ts, and the rest registers it the way #19020 registered bundle.logs.metrics. The non-obvious part is generatePlugin.ts: for bundle_mfe* it no longer injects the two addon bundles, because they overwrite the same keys on window.Sentry, so transport/multiplexed and integrations/moduleMetadata would pass even with both exports missing from the bundle. Locally, the browser unit tests and the full Chromium integration suite with PW_BUNDLE=bundle_mfe and bundle_mfe_min pass.

Unsure about: The name bundle.mfe is the one suggested in the issue, happy to rename. bundle_mfe also adds one job to the Playwright matrix, as #19020 did.

Closes #17309