[ws client]: fix propogate error in subscription response (#356)

* [client types]: fix #349

Subscription::next() propogate error when parsing the response fails

* unify subscription and notification

* rename again

* Update types/src/traits.rs

* fix bad merge

* Update types/src/client.rs

Co-authored-by: David <[email protected]>

* grumbles: subscribe_method -> subscribe_to_method

* Update tests/tests/integration_tests.rs

Co-authored-by: David <[email protected]>

* grumbles: doc links

Co-authored-by: David <[email protected]>