* Revert "Do not register UI-related native functions in secondary isolates (#6401)"

This reverts commit 69ae5694 as it doesn't work when root and secondary isolates run in the same isolate group.

* Confirm it is root isolate that makes UI native calls.

* Fix format, UIDartState reference from Fuchsia source

* No UI isolate check for fuchsia calls

* Fix typo. Remove redundant runtime calls