Add Support for useReactiveVar hook

[nuwanwre]

Add support for useReactiveVar and remove useQuery hook for component level updates. This update needs to done with apollo-client 3.2.0.

Reference: PR

[nuwanwre]

apollo-client 3.2.0 released. Needs integration for useReactiveVar hook.

[nuwanwre]

Apollo Client 3 for React Native uses apollo-cache-persist as it's persistence layer. However, current implementation of ReactVars handles storage outside of the cache, hence persisting ReactiveVars does not function as expected.

A recent issue points out ReactiveVars are not being persisted. However, this PR seems to address the issue pointed out by the mentioned issue, and suggests a workaround for persisting ReactiveVars. Until official support for persisting ReactiveVars is merged, local fields as mentioned here, is a viable option.

Keeping this issue open until there is a stable solution.

Reference implementation