* fix: allow stream protocols to return headers with multiple values
This allows stream protocols to return headers with multiple values as
an array of values.
Fixes https://github.com/electron/electron/issues/14778
* Prefer ConvertFromV8
* Cleanup header conversion
1. Deduplicate the code by using a lambda
2. Remove duplicate calls to headers->Get(key)
* Fix broken test
Headers with multiple values are now being converted correctly, this
test asserted the wrong behavior.
3b6f0d83e1