fix: add handle for resolveExternalUri (#5624)

* fix: add handle for resolveExternalUri

This adds a fix to properly handle `resolveExternalUri` which is used by
extensions like Tabnine.

* fixup!: update patch

* fixup!: force update proxy patch

* fixup!: use proxyEndpointTemplate else manually add

* fixup!: throw error if productConfiguration missing

* feat(testing): add asExternalUri

This modifies the test extension used in e2e test by registering a new
command for testing `asExternalUri`.

* feat: add e2e test for asExternalUri

* docs: update playwright setup comments

* feat: add support for VSCODE_PROXY_URI

* chore: refresh patches

* feat: add test for VSCODE_PROXY_URI

* chore: add metadata to lang extension

* fixup!: fix part of service-worker patch

* fixup!: remove e2e test, update patch notes

* fixup!: refresh disable-downloads

* fixup!: formatting